Non-aqueous electrolyte solution and lithium secondary battery using same

ABSTRACT

A non-aqueous electrolyte solution having a large capacity, exhibits high storage characteristics and cycle characteristics, and is capable if inhibiting gas generation. The non-aqueous electrolyte solution contains a lithium salt and a non-aqueous solvent, and a cyclic carbonate compound having an unsaturated bond in a concentration of 0.01 weight % or higher and 8 weight % or lower; and a compound expressed by a formula (IIb) in a concentration of 0.01 weight % or higher and 5 weight % or lower: 
                         
wherein Z 5  represents an integer of 2 or larger, X 5  represents a linkage group comprising one or more atoms selected from the group consisting of a carbon atom, a hydrogen atom, a fluorine atom and an oxygen atom, and the fluoro sulfonyl group is bound to a carbon atom of the linkage group.

TECHNICAL FIELD

The present invention relates to a non-aqueous electrolyte solution anda lithium secondary battery using the same.

BACKGROUND ART

Non-aqueous electrolyte solution batteries, such as lithium secondarybatteries, are being put to practical use in a wide range of applicationfields from a so-called consumer-oriented power source for a cellularphone, a notebook computer, or the like, to an on-vehicle power sourcefor driving an automobile. However, recent years have been seenincreasing demands for higher performance on the non-aqueous electrolytesolution batteries: it is demanded to achieve excellent cyclecharacteristics in addition to large capacity and a high level ofhigh-temperature-storage characteristics.

Accordingly, in order to obtain a non-aqueous electrolyte solutionbattery with a higher capacity, current designing methods are commonlyintended to cram the largest possible amount of active material into alimited battery volume, such as the method in which pressure is appliedto the active material layer of the electrode so as to increase itsdensity and reduce the space remaining in the electrode. However, if thespace within the battery is diminished, there arises a problem that evenwhen a small amount of gas is generated due to decomposition of theelectrolyte solution, the internal pressure of the battery remarkablyincreases.

Also, when a non-aqueous electrolyte solution battery is used as abackup power source in case of a power failure or a power source of aportable device, in order to compensate for self discharging of thebattery, the battery is continuously supplied with a weak current and isconstantly put in a state of charging. In such a state of continuouscharging, the active materials in the electrodes keep exhibiting a highlevel of activity while, due to heat generated in the device, thecapacity of the battery may acceleratingly decrease or the electrolytesolution may decompose and tend to bring about the generation of gas.Especially in a type of battery that detects an abnormal increase in itsinternal pressure due to abnormalities such as overcharging andactivates a safety valve, generation of a large quantity of gas may alsoactivate the safety valve. On the other hand, in a battery having nosafety valve, the pressure of the generated gas may dilate the batteryand disable the battery per se.

In order to obtain a non-aqueous electrolyte solution battery thatsatisfy various properties required for non-aqueous electrolyte solutionbatteries, including the prevention of gas generation as mentionedabove, various compounds are being examined in search of an additive toa non-aqueous electrolyte solution.

For example, Patent Document 1 discloses that when a non-aqueouselectrolyte solution using an asymmetric chain carbonic ester compoundis used as a non-aqueous solvent while a cyclic carbonic ester compoundhaving double bonds is added thereto, the cyclic carbonic ester compoundhaving double bonds preferentially reacts with a negative electrode toform a coating of good quality over the negative electrode surface, sothat the forming of a non-conductive coating over the negative electrodesurface caused by the asymmetric chain carbonic ester compound isinhibited, and that the resultant secondary battery shows improvementsin its storage characteristics and cycle characteristics.

Patent Document 2 discloses that by adding a carbonic ester compoundhaving ether linkages to a non-aqueous electrolyte solution, thecompound covers active spots on the positive electrode surface,oxidative decomposition of a non-aqueous solvent contained in theelectrolyte solution can be inhibited, so that the resultant secondarybattery shows improvement in its storage stability at high temperatureand high voltage.

Patent Document 3 discloses that adding benzene sulfonyl fluoride orp-toluene sulfonyl fluoride to a non-aqueous electrolyte solutionimproves discharging characteristics at low temperature, so that abattery having excellent cycle characteristics can be obtained.

Patent Document 4 discloses that when an electrolyte solution includesan ether compound having a specific structure containing fluorine atoms,runaway reaction due to overheating does not occur, so that theelectrolyte solution shows improved safety.

Patent Document 5 discloses that when one or more of aromatic compounds,esters, carbonates and monoethers having a specific structure includingfluorines are contained in an electrolyte solution, generation ofhydrogen gas due to decomposition of the electrolyte solution isinhibited at an interface between the positive electrode and theseparator, so that swelling of the battery can be inhibited even in hightemperature surrounding.

Patent Document 6 discloses that when a cyclic ether compound is addedto a non-aqueous electrolyte solution using a mixture of a cycliccarbonic ester and a chain carbonic ester as a non-aqueous solvent, theresultant battery has large capacity and is excellent in cyclecharacteristics.

Patent Document 7 reports that when a compound monomer or polymer whosemolecule contains an amide group is used for forming a coating of anegative electrode, the heat-resistance stability of thenegative-electrode coating can be improved.

[Patent Document 1] Japanese Patent Laid-Open Application No. Hei11-185806

[Patent Document 2] Japanese Patent Laid-Open Application No.2002-237328

[Patent Document 3] Japanese Patent Laid-Open Application No.2002-359001

[Patent Document 4] The pamphlet of International Publication No.00/16427

[Patent Document 5] Japanese Patent Laid-Open Application No.2002-343424

[Patent Document 6] Japanese Patent Laid-Open Application No. Hei10-116631

[Patent Document 7] Japanese Patent Laid-Open Application No. 2003-31260

DISCLOSURE OF THE INVENTION Problem to Be Solved by the Invention

However, as regards a secondary battery using a non-aqueous electrolytesolution containing a cyclic carbonic ester compound having double bondsdisclosed in Patent Document 1, although cycle characteristics at roomtemperature are improved, there are problems in that cyclecharacteristics at low temperature may become deteriorated and that theamount of gas generated during a state of continuous charging mayincrease.

As for a non-aqueous electrolyte solution containing benzene sulfonylfluoride or p-toluene sulfonyl fluoride described in Patent Document 3,there is a problem in that continuous charging characteristics at hightemperature and high-temperature-storage characteristics may bedeteriorated.

Regarding Patent Document 4, it only shows examples in which ethercompounds having fluorines are contained at 60-70 weight % and makes nomention of battery characteristics, so that there is a problem in thatwhen it is actually applied to a battery, battery characteristics suchas continuous charging characteristics may decline.

As to Patent Document 5, there is no mention of cyclic carbonates havingunsaturated bonds and is also silent about continuous chargingcharacteristics at high voltage. It therefore involves a problem in thatcontinuous charging characteristics may actually decrease.

In addition, when an electrolyte solution as disclosed in PatentDocument 4 and Patent Document 5 is used at high voltage, there is aproblem that the battery may be deteriorated and that batterycharacteristics may decline, as will be mentioned later. Specifically,although a battery having lower volume and higher density can berealized by enabling the battery to be charged and discharged by ahigher voltage, when the battery is actually used at a high voltage, theelectrode having a high potential may react with the electrolytesolution to bring about deterioration in the battery and shortening ofthe battery's life.

As regards a monocyclo cyclic ether compound such as 1,3-dioxolane,tetrahydrofuran, tetrahydropyran, or dioxane as described in PatentDocument 6, the present inventors examined it by adding it to anon-aqueous electrolyte solution, as a result of which continuouscharging characteristics (especially, residual capacity after continuouscharging) and high-temperature-storage characteristics were notimproved.

Also, Patent Document 7 only mentions a wide range of compounds having aspecific partial structure containing nitrogen and oxygen, and is silentabout battery characteristics that are of prime importance when beingput in practical use, especially degradation characteristics and gasgeneration during storage.

In recent years, batteries of smaller sizes have been demanded for usessuch as cellular phones, while prevention of swelling has become aproblem of higher importance along with increase in capacity. One of themain causes of such swelling is, in addition to the swelling andshrinking of electrodes and other components, the generation of gasresulting from the decomposition of electrolyte solution or the like.Since the prevention of such swelling enables to develop batteries ofsmaller sizes, further improvements are demanded in order to prevent gasgeneration without impairing other characteristics. When a battery isused in a state of continuous charging with high voltage, there is aproblem in that the electrodes at high potential react with theelectrolyte solution to bring about increase in gas generation,deterioration of the battery, and reduction in the life of the battery.

The present invention has been made in view of the above problems.

An objective of the present invention is to provide a non-aqueouselectrolyte solution that is capable of inhibiting gas generation whileretaining high cycle characteristics, as well as improving continuouscharging characteristics and high-temperature-storage characteristics,and a lithium secondary battery employing the same.

Another objective of the present invention is to provide a non-aqueouselectrolyte solution that is capable of inhibiting deterioration of abattery used with high voltage, and a lithium secondary batteryemploying the same.

Still another objective of the present invention is to provide anon-aqueous electrolyte solution that is capable of inhibitingdeterioration of a battery stored in a discharged state, as well asinhibiting gas generation, and a lithium secondary battery employing thesame.

Means for Solving the Problem

As the result of eager study, the present inventors have found that theproblems can be solved effectively when a non-aqueous electrolytesolution comprising a lithium salt and a non-aqueous solvent furthercomprises a combination of a cyclic carbonate compound with anunsaturated bond (A ingredient) and a compound (I) (B ingredient) havinga specific structure described later, or a compound (II) (C ingredient)with a specific structure described later, and have accomplished thepresent invention.

According to a first aspect of the present invention, there is provideda non-aqueous electrolyte solution comprising: a lithium salt; anon-aqueous solvent; a cyclic carbonate compound having an unsaturatedbond in a concentration of 0.01 weight % or higher and 8 weight % orlower; and a compound expressed by the following general formula (Ia) ina concentration of 0.01 weight % or higher and 5 weight % or lower.

(in the formula (Ia), R¹¹ and R¹² represent, independently of eachother, an organic group that is composed of one or more carbon atoms andhydrogen atoms and may optionally contain one or more oxygen atoms butexcludes unsaturated bonds, provided that at least either R¹¹ or R¹² hasan ether linkage. The total number of carbon atoms of R¹¹ and R¹² isbetween 3 and 18, and the total number of oxygen atoms contained in R¹¹and R¹² is between 1 and 6.)

According to a second aspect of the present invention, there is provideda non-aqueous electrolyte solution comprising: a lithium salt; anon-aqueous solvent; a cyclic carbonate compound having an unsaturatedbond; and a compound expressed by the following general formula (Ib).

(in the formula (Ib), R²¹ represents an alkyl group having 1-12 carbonatoms that may be substituted by a fluorine atom or an alkenyl grouphaving 2-12 carbon atoms that may be substituted by a fluorine atom,wherein the group may have an ether linkage within its chain.)

It is preferable that in the general formula (Ib), R²¹ is an alkyl grouphaving 1-3 carbon atoms that may be substituted by a fluorine atom.

It is also preferable that the concentration of the compound expressedby the general formula (Ib) with respect to the non-aqueous electrolytesolution is 0.001 weight % or higher and 5 weight % or lower.

It is also preferable that the concentration of the cyclic carbonatecompound having an unsaturated bond with respect to the non-aqueouselectrolyte solution is 0.01 weight % or higher and 8 weight % or lower.

According to a third aspect of the present invention, there is provideda non-aqueous electrolyte solution comprising: a lithium salt; anon-aqueous solvent; a cyclic carbonate compound having an unsaturatedbond in a concentration of 0.01 weight % or higher and 8 weight % orlower; and a compound expressed by the following general formula (Ic) ina concentration of 0.01 weight % or higher and 5 weight % or lower.[Chemical Formula 3]CF_(n)H_((3-n))CH₂X³  (Ic)(in the formula (Ic), n represents an integer of 1-3 and X³ represents agroup selected by the groups expressed by the following formulae(Ic-1)-(Ic-4).

in the formulae (Ic-1)-(Ic-4), R³¹-R³⁴ represent, independently of eachother, an alkyl group having 1-20 carbon atoms that may be substitutedby a halogen atom, and Y³ represents a divalent hydrocarbon group having1-10 carbon atoms that may be substituted by a halogen atom.)

It is preferable that in the general formula (Ic), X³ is expressed bythe formula (Ic-2), and in the formula (Ic-2), Y³ is a divalent alkylenegroup having 1-10 carbon atoms that may be substituted by a halogenatom.

It is also preferable that in the general formula (Ic), X³ is expressedby the formula (Ic-3).

It is also preferable that in the general formula (Ic), X³ is expressedby the formula (Ic-4).

It is also preferable that in the formulae (Ic-1)-(Ic-4), each ofR³¹-R³⁴ is an alkyl group having 1-20 carbon atoms substituted by 1-3fluorine atoms.

According to a fourth aspect of the present invention, there is provideda non-aqueous electrolyte solution comprising: a lithium salt; anon-aqueous solvent; and a compound expressed by the following formula(IIa).

It is preferable that the compound expressed by the following formula(IIa) is a compound expressed by the following general formula (IIa′).

(in the formula (IIa′), R⁴¹-R⁴⁴ represent, independently of each other,a hydrogen atom, an alkyl group having 1-12 carbon atoms that may besubstituted by a fluorine atom, an alkenyl group having 2-12 carbonatoms that may be substituted by a fluorine atom, an aryl group having6-12 carbon atoms that may be substituted by a fluorine atom, or anaralkyl group having 7-12 carbon atoms that may be substituted by afluorine atom. The group may have an ether linkage in its chain. R⁴¹ maybe linked with R⁴², and R⁴³ may be linked with R⁴⁴, to form a ring thatmay have an oxygen atom.)

It is also preferable that the concentration of the compound having thestructure expressed by the formula (IIa) with respect to the non-aqueouselectrolyte solution is 0.001 weight % or higher and 5 weight % orlower.

According to a fifth aspect of the present invention, there is provideda non-aqueous electrolyte solution comprising: a lithium salt; anon-aqueous solvent; and a compound expressed by the following generalformula (IIb).

(in the formula (IIb), Z⁵ represents an integer of 2 or larger, X⁵represents a Z⁵ valent linkage group composed of one or more atomsselected from the group consisting of a carbon atom, a hydrogen atom, afluorine atom and an oxygen atom, and the fluoro sulfonyl group is boundto a carbon atom of the linkage group.)

It is preferable that the concentration of the compound expressed by thegeneral formula (IIb) with respect to the non-aqueous electrolytesolution is 0.001 weight % or higher and 5 weight % or lower.

In the aforementioned fourth and fifth aspects of the present invention,it is also preferable that it further comprises a cyclic carbonatecompound having an unsaturated bond in a concentration of 0.01 weight %or higher and 8 weight % or lower with respect to the non-aqueouselectrolyte solution.

According to a sixth aspect of the present invention, there is provideda non-aqueous electrolyte solution comprising: a lithium salt; anon-aqueous solvent; and a compound expressed by the following generalformula (IIc) in a concentration of 0.01 weight % or higher and 4 weight% or lower with respect to the non-aqueous electrolyte solution.

(in the formula (IIc), Z⁶ represents an integer of 2 or larger, X⁶represents a Z⁶-valent hydrocarbon group having 1-6 carbon atoms, R⁶¹represents, independently of each other, an alkyl group having 1-6carbon atoms, and R⁶² represents, independently of each other, an alkylgroup having 1-6 carbon atoms substituted by one or more halogen atoms.Any two or more of R⁶¹ and/or R⁶² may be linked with each other to forma ring.)

It is preferable that it further comprises a cyclic carbonate compoundhaving an unsaturated bond in a concentration of 0.01 weight % or higherand 5 weight % or lower with respect to the non-aqueous electrolytesolution.

In the aforementioned first through sixth aspects of the presentinvention, it is preferable that the cyclic carbonate compound having anunsaturated bond is a compound or a plurality of compounds selected fromthe group consisting of vinylene carbonate, vinyl ethylene carbonate,divinyl ethylene carbonate, vinyl vinylene carbonate and methylenecarbonate.

According to a seventh aspect of the present invention, there isprovided a lithium secondary battery comprising: a non-aqueouselectrolyte solution; and a positive electrode and a negative electrodecapable of absorbing and desorbing lithium ions; wherein the non-aqueouselectrolyte solution is a non-aqueous electrolyte solution according tothe aforementioned first through sixth aspects of the present invention.

ADVANTAGEOUS EFFECTS OF THE INVENTION

With the non-aqueous electrolyte solution according to the first aspectof the present invention, it is possible to provide a battery that has alarge capacity and is excellent in storage characteristics and cyclecharacteristics, as well as to achieve reduction in size and improvementin performance of a lithium secondary battery.

With the non-aqueous electrolyte solution according to the second aspectof the present invention, it is possible to provide a battery that has alarge capacity, is excellent in storage characteristics, loadcharacteristics and cycle characteristics, and inhibits decrease incapacity and gas generation during continuous charging, as well as toachieve reduction in size and improvement in performance of a lithiumsecondary battery.

With the non-aqueous electrolyte solution according to the third aspectof the present invention, it is possible to realize an excellentnon-aqueous electrolyte solution that is capable of inhibitingdeterioration of a battery used with high voltage. Employing thenon-aqueous electrolyte solution, it is also possible to realize anexcellent lithium secondary battery that allows charge and dischargewith high voltage to thereby realize reduction in size and increase indensity.

With the non-aqueous electrolyte solution according to the fourth aspectof the present invention, it is possible to provide a battery that has alarge capacity, is excellent in storage characteristics, loadcharacteristics and cycle characteristics, and inhibits decrease incapacity and gas generation during continuous charging, as well as toachieve reduction in size and improvement in performance of anon-aqueous electrolyte solution battery.

With the non-aqueous electrolyte solution according to the fifth aspectof the present invention, it is possible to provide a battery that has alarge capacity, is excellent in storage characteristics, loadcharacteristics and cycle characteristics, and inhibits decrease incapacity and gas generation during continuous charging, as well as toachieve reduction in size and improvement in performance of anon-aqueous electrolyte solution battery.

With the non-aqueous electrolyte solution according to the sixth aspectof the present invention, it is possible to realize an excellentnon-aqueous electrolyte solution that is capable of inhibitingdeterioration when stored in a discharged state while inhibiting gasgeneration. Employing the non-aqueous electrolyte solution, it is alsopossible to realize an excellent lithium secondary battery.

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be explained indetail, although the present invention should by no means be limited tothe following embodiments and can be embodied with receiving anymodifications unless departing from the gist of the invention.

The first non-aqueous electrolyte solution of the present inventioncomprises a lithium salt and a non-aqueous solvent, characterized inthat it further comprises a cyclic carbonate compound having anunsaturated bond (hereinafter also called “A ingredient”) and a compound(I) (hereinafter also called “B ingredient”) described below.

The second non-aqueous electrolyte solution of the present inventioncomprises a lithium salt and a non-aqueous solvent, characterized inthat it further comprises a compound (II) (hereinafter also called “Cingredient”) described below. In addition, it is preferable to furthercomprise a cyclic carbonate compound having an unsaturated bond(hereinafter also called “D ingredient”).

The lithium secondary battery of the present invention is a lithiumsecondary battery that comprises a non-aqueous electrolyte solution anda positive electrode and a negative electrode capable of absorbing anddesorbing lithium ions, characterized in that the non-aqueouselectrolyte solution is the first non-aqueous electrolyte solution orthe second non-aqueous electrolyte solution of the present invention.

In the following description, explanations will be given first on thefirst non-aqueous electrolyte solution and the second non-aqueouselectrolyte solution of the present invention in turn, and then on thelithium secondary battery of the present invention employing thesesolutions. Incidentally, the first non-aqueous electrolyte solution andthe second non-aqueous electrolyte solution of the present inventionwill be separately called “the non-aqueous electrolyte solution (I)” and“the non-aqueous electrolyte solution (II)”, respectively, whenexplained distinguishingly, while they will be collectively called “thenon-aqueous electrolyte solution of the present invention” whenexplained without particular distinction.

[1: Non-aqueous Electrolyte Solution (I)]

The non-aqueous electrolyte solution (I) comprises a lithium salt, anon-aqueous solvent, a cyclic carbonate compound having an unsaturatedbond (A ingredient), and a compound (I) (B ingredient) described later.

[Electrolyte]

The electrolyte used for the non-aqueous electrolyte solution (I) is notparticularly limited but may be selected arbitrarily from compoundsknown to be usable as an electrolyte for the objective secondarybattery. For use in a lithium secondary battery, a lithium salt isusually used as the electrolyte.

Examples of lithium salts are: inorganic lithium salts such as LiClO₄,LiAsF₆, LiPF₆, Li₂CO₃ and LiBF₄; fluorine-containing organic lithiumsalts such as LiCF₃SO₃, LiN(CF₃SO₂)₂, LiN(C₂F₅SO₂)₂, lithium cyclic1,3-perfluoropropane disulfonyl imide, LiN(CF₃SO₂)(C₄F₉SO₂),LiC(CF₃SO₂)₃, LiPF₄(CF₃)₂, LiPF₄(C₂F₅)₂, LiPF₄ (CF₃SO₂)₂,LiPF₄(C₂F₅SO₂)₂, LiBF₂(CF₃)₂, LiBF₂(C₂F₅)₂, LiBF₂(CF₃SO₂)₂, andLiBF₂(C₂F₅SO₂)₂; oxalate borate salts such as lithiumbis(oxalate)borate, and lithium difluoro oxalate borate; sodium orpotassium salts such as KPF₆, NaPF₆, NaBF₄, and Na₂CF₃SO₃. These may beused either singly or a mixture of two or more. Among them, LiPF₆,LiBF₄, LiCF₃SO₃, LiN(CF₃SO₂)₂, and LiN(C₂F₅SO₂)₂ are preferable, andLiPF₆ and LiBF₄ are especially preferable.

The aforementioned lithium salts may be used either singly or incombination of any two or more in an arbitrary ratio, although acombined use of two or more inorganic lithium salts or a combined use ofan inorganic lithium salt and a fluorine-containing organic lithium saltis desirable because gas generation during continuous charging can beinhibited or because deterioration after high-temperature storage can beprevented. Especially desirable is a combined use of LiPF₆ and LiBF₄ ora combined use of an inorganic lithium salt such as LiPF₆ or LiBF₄ and afluorine-containing organic lithium salt such as LiCF₃SO₃, LiN(CF₃SO₂)₂,or LiN(C₂F₅SO₂)₂. When LiPF₆ and LiBF₄ are combinedly used, it ispreferable that LiBF₄ is contained in a ratio of usually 0.01 weight %or higher and 20 weight % or lower with respect to the whole lithiumsalts. When an inorganic lithium salt such as LiPF₆ or LiBF₄ and afluorine-containing organic lithium salt such as LiCF₃SO₃, LiN(CF₃SO₂)₂,or LiN(C₂F₅SO₂)₂ are combinedly used, it is desirable that theproportion of the inorganic lithium salt with respect to the wholelithium salt is within the range of usually 70 weight % or higher and 99weight % or lower.

The concentration of the lithium salt in the non-aqueous electrolytesolution (I) is within the range of usually 0.5 mol/litre or larger,preferably 0.6 mol/litre or larger, more preferably 0.8 mol/litre orlarger, and usually 3 mol/litre or smaller, preferably 2 mol/litre orsmaller, more preferably 1.5 mol/litre or smaller. When theconcentration is too low, the electric conductivity of the electrolytesolution may be insufficient, while when the concentration is too high,the electric conductivity may decrease due to increase in its viscosityto cause decline in the battery's performance.

[Non-Aqueous Solvent]

As the non-aqueous solvent of the non-aqueous electrolyte solution (I),it is possible to use any compound previously known as a solvent for anon-aqueous electrolyte solution, usually an organic solvent is used.Examples of organic solvents are chain and cyclic carbonates, chain andcyclic carboxylic acid esters, and chain and cyclic ethers.

Examples of cyclic carbonates are alkylene carbonates whose alkylenegroups have 2-4 carbon atoms, such as ethylene carbonate, propylenecarbonate, butylene carbonate, and fluoroethylene carbonate. Among them,ethylene carbonate and propylene carbonate are preferable.

Examples of chain carbonates are dialkyl carbonates whose alkyl groupshave 1-4 carbon atoms, such as dimethyl carbonate, diethyl carbonate,di-n-propyl carbonate, ethyl methyl carbonate, methyl-n-propylcarbonate, and ethyl-n-propyl carbonate. Among them, dimethyl carbonate,diethyl carbonate, and ethyl methyl carbonate are preferable.

Examples of cyclic carboxylic acid esters are γ-butyrolactone andγ-valerolactone.

Examples of chain carboxylic acid esters are methyl acetate, ethylacetate, methyl propionate, ethyl propionate, and methyl butyrate.

Examples of cyclic ethers are tetrahydrofuran and 2-methyltetrahydrofuran.

Examples of chain ethers are diethoxyethane, dimethoxyethane, anddimethoxymethane.

These non-aqueous solvents may be used either any one singly or incombination of any two or more in an arbitrary ratio, although acombined use of two or more compounds is preferable. For example, it isdesirable to use a high-dielectric solvent, such as a cyclic carbonateor a cyclic carboxylic acid ester, in combination with a low-viscositysolvent, such as a chain carbonate or a chain carboxylic acid ester.

When a chain carboxylic acid ester is contained in the non-aqueoussolvent, the proportion of the chain carboxylic acid ester to thenon-aqueous solvent is usually 50 weight % or lower, preferably 30weight % or lower, more preferably 20 weight % or lower. If theproportion exceeds the upper limit, a decline in conductivity may occur.Note that the chain carboxylic acid ester is not an essential ingredientof the non-aqueous solvent, and that the non-aqueous solvent may containno chain carboxylic acid ester.

When a cyclic carboxylic acid ester is contained in the non-aqueoussolvent, the proportion of the cyclic carboxylic acid ester to thenon-aqueous solvent is usually 60 weight % or lower, preferably 55weight % or lower, more preferably 50 weight % or lower. If theproportion exceeds the upper limit, a decline in immersivity ordegradation in output characteristics at low temperature may occur. Notethat the cyclic carboxylic acid ester is not an essential ingredient ofthe non-aqueous solvent, and that the non-aqueous solvent may contain nocyclic carboxylic acid ester.

When a chain ethers is contained in the non-aqueous solvent, theproportion of the chain ether to the non-aqueous solvent is usually 60weight % or lower, preferably 40 weight % or lower, more preferably 30weight % or lower. If the proportion exceeds the upper limit, a declinein conductivity may occur. Note that the chain ether is not an essentialingredient of the non-aqueous solvent, and that the non-aqueous solventmay contain no chain ether.

When a cyclic ether is contained in the non-aqueous solvent, theproportion of the cyclic ether to the non-aqueous solvent is usually 60weight % or lower, preferably 50 weight % or lower, more preferably 40weight % or lower. If the proportion exceeds the upper limit, a declinein storage characteristics may occur. Note that the cyclic ether is notan essential ingredient of the non-aqueous solvent, and that thenon-aqueous solvent may contain no cyclic ether.

One of the desirable combinations of non-aqueous solvents is a mixturemainly consisting of a cyclic carbonate and a chain carbonate. It isespecially preferable that the total proportion of the cyclic carbonateand the chain carbonate in the non-aqueous solvent is usually 85 volume% or larger, preferably 90 volume % or larger, more preferably 95 volume% or larger and that the volume ratio between the cyclic carbonate andthe chain carbonate is usually 5:95 or higher, preferably 10:90 orhigher, more preferably 15:85 or higher and usually 45:55 or lower,preferably 40:60 or lower. Using the aforementioned mixture solventtogether with an electrolyte, such as a lithium salt, a cyclic carbonatecompound having an unsaturated bond (A ingredient), and a compound (I)(B ingredient) to prepare a non-aqueous electrolyte solution (I) ispreferable because it is possible to adjust the balance betweencharacteristics, such as cycle characteristics and large currentdischarging characteristics, and inhibition of gas generation.

Preferable examples of the combinations between cyclic carbonates andchain carbonates are combinations of ethylene carbonate and dialkylcarbonates. Specifically, there can be mentioned the combination ofethylene carbonate and dimethyl carbonate, the combination of ethylenecarbonate and diethyl carbonate, the combination of ethylene carbonateand ethyl methyl carbonate, the combination of ethylene carbonate,dimethyl carbonate and diethyl carbonate, the combination of ethylenecarbonate, dimethyl carbonate and ethyl methyl carbonate, thecombination of ethylene carbonate, diethyl carbonate and ethyl methylcarbonate, the combination of ethylene carbonate, dimethyl carbonate,diethyl carbonate and ethyl methyl carbonate, etc.

The addition of propylene carbonate to these combinations of ethylenecarbonate and dialkyl carbonates gives other preferable combinations. Inthis case, the volume ratio between ethylene carbonate and propylenecarbonate is usually 99:1 or lower, preferably 95:5 or lower and usually1:99 or higher, preferably 20:80 or higher.

The combinations of propylene carbonate and the aforementioned dialkylcarbonates are also preferable.

Other examples of the non-aqueous solvent are the ones that contain anorganic solvent selected from the group consisting of ethylenecarbonate, propylene carbonate, γ-butyrolactone, and γ-valerolactone inthe ratio of 60 volume % or larger. Using one of these mixture solventstogether with an electrolyte, such as a lithium salt, a cyclic carbonatecompound having an unsaturated bond (A ingredient), and compound (I) (Bingredient), the resultant non-aqueous electrolyte solution (I) cansuppress vaporization and leakage of solvents when used at hightemperature. Preferable among these are: the ones in which the totalvolume of ethylene carbonate and γ-butyrolactone with respect to thenon-aqueous solvent is 80 volume % or larger, preferably 90 volume % orlarger, and the volume ratio of ethylene carbonate to γ-butyrolactone isbetween 5:95 and 45:55; and the ones in which the total volume ofethylene carbonate and propylene carbonate with respect to thenon-aqueous solvent is 80 volume % or larger, preferably 90 volume % orlarger, and the volume ratio of ethylene carbonate to propylenecarbonate is between 30:70 and 80:20. Using one of these mixturesolvents together with an electrolyte, such as a lithium salt, a cycliccarbonate compound having an unsaturated bond (A ingredient), and acompound (I) (B ingredient) to prepare a non-aqueous electrolytesolution (I) is preferable because it can give fine balance betweenstorage characteristics and gas generation inhibition.

It is also preferable to use a phosphorus-containing organic solvent forthe non-aqueous solvent. By adding a phosphorus-containing organicsolvent to the non-aqueous solvent at a ratio of usually 10 volume % orlarger, preferably between 10-80 volume %, it is possible to reduce thecombustibility of the electrolyte solution. It is especially preferableto use a phosphorus-containing organic solvent in combination with anon-aqueous solvent selected from the group consisting of ethylenecarbonate, propylene carbonate, γ-butyrolactone, γ-valerolactone anddialkyl carbonate because cycle characteristics and large currentdischarging characteristics are well-balanced.

Incidentally, in the present description, the volume of a non-aqueoussolvent means a value measured at 25° C. in principle: as theexceptions, for a solvent that is in the solid state at 25° C., such asethylene carbonate, it means a value measured at the melting point.

[Unsaturated Cyclic Carbonate Compound (A Ingredient)]

The non-aqueous electrolyte solution (I) contains a cyclic carbonatecompound having an unsaturated bond (in the present description, it maybe abbreviated as “unsaturated cyclic carbonate compound”) as Aingredient. The term “unsaturated cyclic carbonate compound” means acompound that has at least one carbonate structure, at least onecarbon-carbon double bond, and at least one cyclic structure in a singlemolecule.

As examples of unsaturated cyclic carbonate compounds are vinylenecarbonate compounds, vinyl ethylene carbonate compounds, and methyleneethylene carbonate compounds, although any compound can be used as longas it falls within the above definition.

Examples of vinylene carbonate compounds are vinylene carbonate(hereinafter may be abbreviated as “VC”), methyl vinylene carbonate,ethyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, 4,5-diethylvinylene carbonate, fluoro vinylene carbonate, trifluoromethyl vinylenecarbonate, 4-vinyl vinylene carbonate, etc.

Examples of vinyl ethylene carbonate compounds are vinyl ethylenecarbonate, 4-methyl-4-vinyl ethylene carbonate, 4-ethyl-4-vinyl ethylenecarbonate, 4-n-propyl-4-vinyl ethylene carbonate, 5-methyl-4-vinylethylene carbonate, 4,4-divinyl ethylene carbonate, 4,5-divinyl ethylenecarbonate, etc.

Examples of methylene ethylene carbonate compounds are methyleneethylene carbonate, 4,4-dimethyl-5-methylene ethylene carbonate,4,4-diethyl-5-methylene ethylene carbonate, etc.

Among these, preferable unsaturated cyclic carbonate compounds arevinylene carbonate and vinyl ethylene carbonate, especially preferablebeing vinylene carbonate.

These unsaturated cyclic carbonate compounds may be used either any onesingly or in combination of any two or more at an arbitrary ratio.

The proportion of the unsaturated cyclic carbonate compound in thenon-aqueous electrolyte solution (I) is usually 0.01 weight % or higher,preferably 0.1 weight % or higher, especially preferably 0.5 weight % orhigher, most preferably 1 weight % or higher, and usually 8 weight % orlower, preferably 6 weight % or lower, especially preferably 4 weight %or lower. If the volume of the unsaturated cyclic carbonate compound isbelow the lower limit, it is difficult to form an adequate amount ofnegative electrode coating, which is explained later, and may result indeterioration. On the other hand, if the volume exceeds the upper limit,an excessive amount of negative electrode coating may be formed andprevent the migration of lithium ions. When two or more unsaturatedcyclic carbonate compounds are used in combination, the total volume ofthe unsaturated cyclic carbonate compounds should meet the above range.

[Compound (I) (B Ingredient)]

The non-aqueous electrolyte solution (I) contains, as B ingredient, atleast one compound of a compound (Ia), a compound (Ib), and a compound(Ic) explained below (hereinafter also called “compound (I)”). Thenon-aqueous electrolyte solution (I) may contain any one of the compound(Ia), the compound (Ib) and the compound (Ic) singly, or may contain twoor three of them in combination. In the following description, thenon-aqueous electrolyte solutions (I) that each contain a respective oneof the compound (Ia), the compound (Ib), and the compound (Ic) will berespectively called the “non-aqueous electrolyte solution (Ia)” throughthe “non-aqueous electrolyte solution (Ic)” when explained separately,while they will be collectively called the “non-aqueous electrolytesolution (I)” when explained without particular distinction.

<Compound (Ia)>

The compound (Ia) is a compound expressed by the following generalformula (Ia).

In the general formula (Ia), R¹¹ and R¹² represents, independently ofeach other, an organic group that is composed of one or more carbonatoms and hydrogen atoms and may optionally contain one or more oxygenatoms but excludes unsaturated bonds, provided that at least either R¹¹or R¹² has an ether linkage. The total number of carbon atoms of R¹¹ andR¹² is between 3 and 18, and the total number of oxygen atoms containedin R¹¹ and R¹² is between 1 and 6. It is preferable that the totalnumber of carbon atoms of R¹¹ and R¹² is between 3 and 10, and that thetotal number of oxygen atoms contained in R¹¹ and R¹² is between 1 and4.

It is preferable that each of R¹¹ and R¹² is an alkyl group or an alkylgroup having an ether linkage. Preferable alkyl groups are methyl groupand ethyl group, while preferable alkyl groups having an ether linkageare methoxy alkyl groups and ethoxy alkyl groups. It is also preferablethat R¹¹ and R¹² are different with each other, especially preferablyeither R¹¹ or R¹² being a methyl group.

As the compound (Ia), the followings can be mentioned.

(a) Carbonic esters having one ether linkage per molecule:

Examples of carbonic esters having one ether linkage per moleculeinclude (methyl)(methoxymethyl)carbonate,(methyl)(1-methoxyethyl)carbonate, (methyl)(2-methoxyethyl)carbonate,(methyl)(1-methoxypropyl)carbonate, (methyl)(2-methoxypropyl)carbonate,(methyl)(3-methoxypropyl) carbonate,(methyl)(1-methyl-1-methoxyethyl)carbonate,(methyl)(1-methyl-2-methoxyethyl)carbonate,(methyl)(1-methoxybutyl)carbonate, (methyl)(2-methoxybutyl)carbonate,(methyl)(3-methoxybutyl)carbonate, (methyl)(4-methoxybutyl)carbonate,(methyl)[1-(methoxymethyl)propyl]carbonate,(methyl)(1-methyl-2-methoxypropyl)carbonate,(methyl)(ethoxymethyl)carbonate, (methyl)(1-ethoxyethyl)carbonate,(methyl)(2-ethoxyethyl)carbonate, (methyl)(1-ethoxypropyl)carbonate,(methyl)(2-ethoxypropyl)carbonate, (methyl)(3-ethoxypropyl)carbonate,(methyl)(1-methyl-1-ethoxyethyl)carbonate,(methyl)(1-methyl-2-ethoxyethyl)carbonate,(methyl)(1-ethoxybutyl)carbonate, (methyl)(2-ethoxybutyl)carbonate,(methyl)(3-ethoxybutyl)carbonate, (methyl)(4-ethoxybutyl)carbonate,(methyl)[1-(ethoxymethyl)propyl]carbonate,(methyl)(1-methyl-2-ethoxypropyl)carbonate,(methyl)(butoxymethyl)carbonate, (methyl)(1-butoxyethyl)carbonate,(methyl)(2-butoxyethyl)carbonate, (methyl)(1-butoxypropyl)carbonate,(methyl)(2-butoxypropyl)carbonate, (methyl)(3-butoxypropyl)carbonate,(methyl)(1-methyl-1-butoxyethyl)carbonate,(methyl)(1-methyl-2-butoxyethyl)carbonate,(methyl)(1-butoxybutyl)carbonate, (methyl)(2-butoxybutyl)carbonate,(methyl)(3-butoxybutyl)carbonate, (methyl)(4-butoxybutyl)carbonate,(methyl)[1-(butoxymethyl)propyl]carbonate,(methyl)(1-methyl-2-butoxypropyl)carbonate,(methyl)(tetrahydrofurfuryl)carbonate,(methyl)(tetrahydropyranylmethyl)carbonate,(ethyl)(methoxymethyl)carbonate, (ethyl)(1-methoxyethyl)carbonate,(ethyl)(2-methoxyethyl)carbonate, (ethyl)(1-methoxypropyl)carbonate,(ethyl)(2-methoxypropyl)carbonate, (ethyl)(3-methoxypropyl)carbonate,(ethyl)(1-methyl-1-methoxyethyl)carbonate,(ethyl)(1-methyl-2-methoxyethyl)carbonate,(ethyl)(1-methoxybutyl)carbonate, (ethyl)(2-methoxybutyl)carbonate,(ethyl)(3-methoxybutyl)carbonate, (ethyl)(4-methoxybutyl)carbonate,(ethyl)[1-(methoxymethyl)propyl]carbonate,(ethyl)(1-methyl-2-methoxypropyl)carbonate,(ethyl)(ethoxymethyl)carbonate, (ethyl)(1-ethoxyethyl)carbonate,(ethyl)(2-ethoxyethyl)carbonate, (ethyl)(1-ethoxypropyl)carbonate,(ethyl)(2-ethoxypropyl)carbonate, (ethyl)(3-ethoxypropyl)carbonate,(ethyl)(1-methyl-1-ethoxyethyl)carbonate,(ethyl)(1-methyl-2-ethoxyethyl)carbonate,(ethyl)(1-ethoxybutyl)carbonate, (ethyl)(2-ethoxybutyl)carbonate,(ethyl)(3-ethoxybutyl)carbonate, (ethyl)(4-ethoxybutyl)carbonate,(ethyl)[1-(ethoxymethyl)propyl]carbonate,(ethyl)(1-methyl-2-ethoxypropyl)carbonate,(ethyl)(butoxymethyl)carbonate, (ethyl)(1-butoxyethyl)carbonate,(ethyl)(2-butoxyethyl)carbonate, (ethyl)(1-butoxypropyl)carbonate,(ethyl)(2-butoxypropyl)carbonate, (ethyl)(3-butoxypropyl)carbonate,(ethyl)(1-methyl-1-butoxyethyl)carbonate,(ethyl)(1-methyl-2-butoxyethyl)carbonate,(ethyl)(1-butoxybutyl)carbonate, (ethyl)(2-butoxybutyl)carbonate,(ethyl)(3-butoxybutyl)carbonate, (ethyl)(4-butoxybutyl)carbonate,(ethyl)[1-(butoxymethyl)propyl]carbonate,(ethyl)(1-methyl-2-butoxypropyl)carbonate,(ethyl)(tetrahydrofurfuryl)carbonate,(ethyl)(tetrahydropyranylmethyl)carbonate,(butyl))(methoxymethyl)carbonate, (butyl)(1-methoxyethyl)carbonate,(butyl)(2-methoxyethyl)carbonate, (butyl)(1-methoxypropyl)carbonate,(butyl)(2-methoxypropyl)carbonate, (butyl)(3-methoxypropyl)carbonate,(butyl)(1-methyl-1-methoxyethyl)carbonate,(butyl)(1-methyl-2-methoxyethyl)carbonate,(butyl)(1-methoxybutyl)carbonate, (butyl)(2-methoxybutyl)carbonate,(butyl)(3-methoxybutyl)carbonate, (butyl)(4-methoxybutyl)carbonate,(butyl)[1-(methoxymethyl)propyl]carbonate,(butyl)(1-methyl-2-methoxypropyl)carbonate,(butyl)(ethoxymethyl)carbonate, (butyl)(1-ethoxyethyl)carbonate,(butyl)(2-ethoxyethyl)carbonate, (butyl)(1-ethoxypropyl)carbonate,(butyl)(2-ethoxypropyl)carbonate, (butyl)(3-ethoxypropyl)carbonate,(butyl)(1-methyl-1-ethoxyethyl)carbonate,(butyl)(1-methyl-2-ethoxyethyl)carbonate,(butyl)(1-ethoxybutyl)carbonate, (butyl)(2-ethoxybutyl)carbonate,(butyl)(3-ethoxybutyl)carbonate, (butyl)(4-ethoxybutyl)carbonate,(butyl)[1-(ethoxymethyl)propyl]carbonate,(butyl)(1-methyl-2-ethoxypropyl)carbonate,(butyl)(butoxymethyl)carbonate, (butyl)(1-butoxyethyl)carbonate,(butyl)(2-butoxyethyl)carbonate, (butyl)(1-butoxypropyl)carbonate,(butyl)(2-butoxypropyl)carbonate, (butyl)(3-butoxypropyl)carbonate,(butyl)(1-methyl-1-butoxyethyl)carbonate,(butyl)(1-methyl-2-butoxyethyl)carbonate,(butyl)(1-butoxybutyl)carbonate, (butyl)(2-butoxybutyl)carbonate,(butyl)(3-butoxybutyl)carbonate, (butyl)(4-butoxybutyl)carbonate,(butyl)[1-(butoxymethyl)propyl]carbonate,(butyl)(1-methyl-2-butoxypropyl)carbonate,(butyl)(tetrahydrofurfuryl)carbonate,(butyl)(tetrahydropyranylmethyl)carbonate,(hexyl)(methoxymethyl)carbonate, (hexyl)(1-methoxyethyl)carbonate,(hexyl)(2-methoxyethyl)carbonate, (hexyl)(1-methoxypropyl)carbonate,(hexyl)(2-methoxypropyl)carbonate, (hexyl)(3-methoxypropyl)carbonate,(hexyl)(1-methyl-1-methoxyethyl)carbonate,(hexyl)(1-methyl-2-methoxyethyl)carbonate,(hexyl)(1-methoxybutyl)carbonate, (hexyl)(2-methoxybutyl)carbonate,(hexyl)(3-methoxybutyl)carbonate, (hexyl)(4-methoxybutyl)carbonate,(hexyl)[1-(methoxymethyl)propyl]carbonate,(hexyl)(1-methyl-2-methoxypropyl)carbonate,(hexyl)(ethoxymethyl)carbonate, (hexyl)(1-ethoxyethyl)carbonate,(hexyl)(2-ethoxyethyl)carbonate, (hexyl)(1-ethoxypropyl)carbonate,(hexyl)(2-ethoxypropyl)carbonate, (hexyl)(3-ethoxypropyl)carbonate,(hexyl)(1-methyl-1-ethoxyethyl)carbonate,(hexyl)(1-methyl-2-ethoxyethyl)carbonate,(hexyl)(1-ethoxybutyl)carbonate, (hexyl)(2-ethoxybutyl)carbonate,(hexyl)(3-ethoxybutyl)carbonate, (hexyl)(4-ethoxybutyl)carbonate,(hexyl)[1-(ethoxymethyl)propyl]carbonate,(hexyl)(1-methyl-2-ethoxypropyl)carbonate,(hexyl)(butoxymethyl)carbonate, (hexyl)(1-butoxyethyl)carbonate,(hexyl)(2-butoxyethyl)carbonate, (hexyl)(1-butoxypropyl)carbonate,(hexyl)(2-butoxypropyl)carbonate, (hexyl)(3-butoxypropyl)carbonate,(hexyl)(1-methyl-1-butoxyethyl)carbonate,(hexyl)(1-methyl-2-butoxyethyl)carbonate,(hexyl)(1-butoxybutyl)carbonate, (hexyl)(2-butoxybutyl)carbonate,(hexyl)(3-butoxybutyl)carbonate, (hexyl)(4-butoxybutyl)carbonate,(hexyl)[1-(butoxymethyl)propyl]carbonate,(hexyl)(1-methyl-2-butoxypropyl)carbonate,(hexyl)(tetrahydrofurfuryl)carbonate, and(hexyl)(tetrahydropyranylmethyl)carbonate.

Preferable among them are (methyl)(2-methoxyethyl)carbonate,(methyl)(3-methoxypropyl)carbonate, (methyl)(4-methoxybutyl)carbonate,(methyl)(2-ethoxyethyl)carbonate, (methyl)(3-ethoxypropyl)carbonate,(methyl)(4-ethoxybutyl)carbonate, (methyl)(2-butoxyethyl)carbonate,(methyl)(3-butoxypropyl)carbonate, (methyl)(4-butoxybutyl)carbonate,(methyl)(tetrahydrofurfuryl)carbonate,(methyl)(tetrahydropyranylmethyl)carbonate,(ethyl)(2-methoxyethyl)carbonate, (ethyl)(3-methoxypropyl)carbonate,(ethyl)(4-methoxybutyl)carbonate, (ethyl)(2-ethoxyethyl)carbonate,(ethyl)(3-ethoxypropyl)carbonate, (ethyl)(4-ethoxybutyl)carbonate,(ethyl)(2-butoxyethyl)carbonate, (ethyl)(3-butoxypropyl)carbonate,(ethyl)(4-butoxybutyl)carbonate, (ethyl)(tetrahydrofurfuryl)carbonate,and (ethyl)(tetrahydropyranylmethyl)carbonate.

Especially preferable among them are (methyl)(2-methoxyethyl)carbonate,(methyl)(3-methoxypropyl)carbonate, (methyl)(4-methoxybutyl)carbonate,(methyl)(2-ethoxyethyl)carbonate, (methyl)(3-ethoxypropyl)carbonate,(methyl)(4-ethoxybutyl)carbonate, (ethyl)(2-methoxyethyl)carbonate,(ethyl)(3-methoxypropyl)carbonate, (ethyl)(4-methoxybutyl)carbonate,(ethyl)(2-ethoxyethyl)carbonate, (ethyl)(3-ethoxypropyl)carbonate, and(ethyl)(4-ethoxybutyl)carbonate.

(b) Carbonic esters having two ether linkages per molecule:

Examples of carbonic esters having two ether linkages per moleculeinclude bis(methoxymethyl)carbonate, bis(1-methoxyethyl)carbonate,bis(2-methoxyethyl)carbonate, bis(1-methoxypropyl)carbonate,bis(2-methoxypropyl)carbonate, bis(3-methoxypropyl)carbonate,bis(1-methyl-1-methoxyethyl)carbonate,bis(1-methyl-2-methoxyethyl)carbonate, bis(1-methoxybutyl)carbonate,bis(2-methoxybutyl)carbonate, bis(3-methoxybutyl)carbonate,bis(4-methoxybutyl)carbonate, bis[1-(methoxymethyl)propyl]carbonate,bis(1-methyl-2-methoxypropyl)carbonate, bis(ethoxymethyl)carbonate,bis(1-ethoxyethyl)carbonate, bis(2-ethoxyethyl)carbonate,bis(1-ethoxypropyl)carbonate, bis(2-ethoxypropyl)carbonate,bis(3-ethoxypropyl)carbonate, bis(1-methyl-1-ethoxyethyl)carbonate,bis(1-methyl-2-ethoxyethyl)carbonate, bis(1-ethoxybutyl)carbonate,bis(2-ethoxybutyl)carbonate, bis(3-ethoxybutyl)carbonate,bis(4-ethoxybutyl)carbonate, bis[1-(ethoxymethyl)propyl]carbonate,bis(1-methyl-2-ethoxypropyl)carbonate, bis(butoxymethyl)carbonate,bis(1-butoxyethyl)carbonate, bis(2-butoxyethyl)carbonate,bis(1-butoxypropyl)carbonate, bis(2-butoxypropyl)carbonate,bis(3-butoxypropyl)carbonate, bis(1-methyl-1-butoxyethyl)carbonate,bis(1-methyl-2-butoxyethyl)carbonate, bis(tetrahydrofurfuryl)carbonate,bis(tetrahydropyranylmethyl)carbonate,(methyl)[2-(2-methoxyethoxy)ethyl]carbonate,(methyl)[2-(2-ethoxyethoxy)ethyl]carbonate,(methyl)[2-(2-butoxyethoxy)ethyl]carbonate,(methyl)[2-(2-methoxyethoxy)propyl]carbonate,(methyl)[2-(2-ethoxyethoxy)propyl]carbonate,(methyl)[2-(2-butoxyethoxy)propyl]carbonate,(methyl)[3-(2-methoxyethoxy)propyl]carbonate,(methyl)[3-(2-ethoxyethoxy)propyl]carbonate,(methyl)[3-(2-butoxyethoxy)propyl]carbonate,(methyl)[4-(2-methoxyethoxy)butyl]carbonate,(methyl)[4-(2-ethoxyethoxy)butyl]carbonate,(methyl)[4-(2-butoxyethoxy)butyl]carbonate,(methyl)[2-(2-methoxybutoxy)ethyl]carbonate,(methyl)[2-(2-ethoxybutoxy)ethyl]carbonate,(methyl)[2-(2-butoxybutoxy)ethyl]carbonate,(methyl)[2-(2-methoxybutoxy)propyl]carbonate,(methyl)[2-(2-ethoxybutoxy)propyl]carbonate,(methyl)[2-(2-butoxybutoxy)propyl]carbonate,(methyl)[3-(2-methoxybutoxy)propyl]carbonate,(methyl)[3-(2-ethoxybutoxy)propyl]carbonate,(methyl)[3-(2-butoxybutoxy)propyl]carbonate,(methyl)[4-(2-methoxybutoxy)butyl]carbonate,(methyl)[4-(2-ethoxybutoxy)butyl]carbonate,(methyl)[4-(2-butoxybutoxy)butyl]carbonate,(ethyl)[2-(2-methoxyethoxy)ethyl]carbonate,(ethyl)[2-(2-ethoxyethoxy)ethyl]carbonate,(ethyl)[2-(2-butoxyethoxy)ethyl]carbonate,(ethyl)[2-(2-methoxyethoxy)propyl]carbonate,(ethyl)[2-(2-ethoxyethoxy)propyl]carbonate,(ethyl)[2-(2-butoxyethoxy)propyl]carbonate,(ethyl)[3-(2-methoxyethoxy)propyl]carbonate,(ethyl)[3-(2-ethoxyethoxy)propyl]carbonate,(ethyl)[3-(2-butoxyethoxy)propyl]carbonate,(ethyl)[4-(2-methoxyethoxy)butyl]carbonate,(ethyl)[4-(2-ethoxyethoxy)butyl]carbonate,(ethyl)[4-(2-butoxyethoxy)butyl]carbonate,(ethyl)[2-(2-methoxybutoxy)ethyl]carbonate,(ethyl)[2-(2-ethoxybutoxy)ethyl]carbonate,(ethyl)[2-(2-butoxybutoxy)ethyl]carbonate,(ethyl)[2-(2-methoxybutoxy)propyl]carbonate,(ethyl)[2-(2-ethoxybutoxy)propyl]carbonate,(ethyl)[2-(2-butoxybutoxy)propyl]carbonate,(ethyl)[3-(2-methoxybutoxy)propyl]carbonate,(ethyl)[3-(2-ethoxybutoxy)propyl]carbonate,(ethyl)[3-(2-butoxybutoxy)propyl]carbonate,(ethyl)[4-(2-methoxybutoxy)butyl]carbonate,(ethyl))[4-(2-ethoxybutoxy)butyl]carbonate,(ethyl)[4-(2-butoxybutoxy)butyl]carbonate,(butyl)[2-(2-methoxyethoxy)ethyl]carbonate,(butyl)[2-(2-ethoxyethoxy)ethyl]carbonate,(butyl)[2-(2-butoxyethoxy)ethyl]carbonate,(butyl)[2-(2-methoxyethoxy)propyl]carbonate,(butyl)[2-(2-ethoxyethoxy)propyl]carbonate,(butyl)[2-(2-butoxyethoxy)propyl]carbonate,(butyl)[3-(2-methoxyethoxy)propyl]carbonate,(butyl)[3-(2-ethoxyethoxy)propyl]carbonate,(butyl)[3-(2-butoxyethoxy)propyl]carbonate,(butyl)[4-(2-methoxyethoxy)butyl]carbonate,(butyl)[4-(2-ethoxyethoxy)butyl]carbonate,(butyl)[4-(2-butoxyethoxy)butyl]carbonate,(butyl)[2-(2-methoxybutoxy)ethyl]carbonate,(butyl)[2-(2-ethoxybutoxy)ethyl]carbonate,(butyl)[2-(2-butoxybutoxy)ethyl]carbonate,(butyl)[2-(2-methoxybutoxy)propyl]carbonate,(butyl)[2-(2-ethoxybutoxy)propyl]carbonate,(butyl)[3-(2-methoxybutoxy)propyl]carbonate,(butyl)[3-(2-ethoxybutoxy)propyl]carbonate,(hexyl)[2-(2-methoxyethoxy)ethyl]carbonate,(hexyl)[2-(2-ethoxyethoxy)ethyl]carbonate,(hexyl)[2-(2-butoxyethoxy)ethyl]carbonate,(hexyl)[2-(2-methoxyethoxy)propyl]carbonate,(hexyl)[2-(2-ethoxyethoxy)propyl]carbonate,(hexyl)[3-(2-methoxyethoxy)propyl]carbonate,(hexyl)[3-(2-ethoxyethoxy)propyl]carbonate,(hexyl)[4-(2-methoxyethoxy)butyl]carbonate,(hexyl)[4-(2-ethoxyethoxy)butyl]carbonate,(hexyl)[2-(2-methoxybutoxy)ethyl]carbonate,(hexyl)[2-(2-ethoxybutoxy)ethyl]carbonate,(hexyl)[2-(2-methoxybutoxy)propyl]carbonate, and(hexyl)[3-(2-methoxybutoxy)propyl]carbonate.

Preferable among them are bis(2-methoxyethyl)carbonate,bis(3-methoxypropyl)carbonate, bis(4-methoxybutyl)carbonate,bis(2-ethoxyethyl)carbonate, bis(3-ethoxypropyl)carbonate,bis(4-ethoxybutyl)carbonate, bis(2-butoxyethyl)carbonate,bis(3-butoxypropyl)carbonate, bis(4-butoxybutyl)carbonate,bis(tetrahydrofurfuryl)carbonate,(methyl)[2-(2-methoxyethoxy)ethyl]carbonate,(methyl)[2-(2-ethoxyethoxy)ethyl]carbonate,(methyl)[2-(2-butoxyethoxy)ethyl]carbonate,(ethyl)[2-(2-methoxyethoxy)ethyl]carbonate,(ethyl)[2-(2-ethoxyethoxy)ethyl]carbonate, and(ethyl)[2-(2-butoxyethoxy)ethyl]carbonate.

Especially preferable among them are bis(2-methoxyethyl)carbonate,bis(3-methoxypropyl)carbonate, bis(4-methoxybutyl)carbonate,bis(2-ethoxyethyl)carbonate, bis(3-ethoxypropyl)carbonate,bis(4-ethoxybutyl)carbonate,(methyl)[2-(2-methoxyethoxy)ethyl]carbonate,(methyl)[2-(2-ethoxyethoxy)ethyl]carbonate,(ethyl)[2-(2-methoxyethoxy)ethyl]carbonate, and(ethyl)[2-(2-ethoxyethoxy)ethyl]carbonate.

(c) Carbonic esters having three ether linkages per molecule:

Examples of carbonic esters having three ether linkages per moleculeinclude (methyl)[2-(2-(2-methoxyethoxy)ethoxy)ethyl]carbonate,(methyl)[2-(2-(2-ethoxyethoxy)ethoxy)ethyl]carbonate,(methyl)[2-(2-(2-butoxyethoxy)ethoxy)ethyl]carbonate,(ethyl)[2-(2-(2-methoxyethoxy)ethoxy)ethyl]carbonate,(ethyl)[2-(2-(2-ethoxyethoxy)ethoxy)ethyl]carbonate,(ethyl)[2-(2-(2-butoxyethoxy)ethoxy)ethyl]carbonate,(hexyl)[2-(2-(2-methoxyethoxy)ethoxy)ethyl]carbonate,(hexyl)[2-(2-(2-ethoxyethoxy)ethoxy)ethyl]carbonate,(2-methoxyethyl)[2-(2-methoxyethoxy)ethyl]carbonate,(2-methoxyethyl)[2-(2-ethoxyethoxy)ethyl]carbonate,(2-methoxyethyl)[2-(2-butoxyethoxy)ethyl]carbonate,(2-methoxyethyl)[2-(2-methoxyethoxy)propyl]carbonate,(2-methoxyethyl)[2-(2-ethoxyethoxy)propyl]carbonate,(2-methoxyethyl)[2-(2-butoxyethoxy)propyl]carbonate,(2-methoxyethyl)[3-(2-methoxyethoxy)propyl]carbonate,(2-methoxyethyl)[3-(2-ethoxyethoxy)propyl]carbonate,(2-methoxyethyl)[3-(2-butoxyethoxy)propyl]carbonate,(2-methoxyethyl)[4-(2-methoxyethoxy)butyl]carbonate,(2-methoxyethyl)[4-(2-ethoxyethoxy)butyl]carbonate,(2-methoxyethyl)[4-(2-butoxyethoxy)butyl]carbonate,(2-methoxyethyl)[2-(2-methoxybutoxy)ethyl]carbonate,(2-methoxyethyl)[2-(2-ethoxybutoxy)ethyl]carbonate,(2-methoxyethyl)[2-(2-butoxybutoxy)ethyl]carbonate,(2-methoxyethyl)[2-(2-methoxybutoxy)propyl]carbonate,(2-methoxyethyl)[2-(2-ethoxybutoxy)propyl]carbonate,(2-methoxyethyl)[2-(2-butoxybutoxy)propyl]carbonate,(2-methoxyethyl)[3-(2-methoxybutoxy)propyl]carbonate,(2-methoxyethyl)[3-(2-ethoxybutoxy)propyl]carbonate,(2-methoxyethyl)[3-(2-butoxybutoxy)propyl]carbonate,(2-methoxyethyl)[4-(2-methoxybutoxy)butyl]carbonate,(2-methoxyethyl)[4-(2-ethoxybutoxy)butyl]carbonate,(2-ethoxyethyl)[2-(2-methoxyethoxy)ethyl]carbonate,(2-ethoxyethyl)[2-(2-ethoxyethoxy)ethyl]carbonate,(2-ethoxyethyl)[2-(2-butoxyethoxy)ethyl]carbonate,(2-ethoxyethyl)[2-(2-methoxyethoxy)propyl]carbonate,(2-ethoxyethyl)[2-(2-ethoxyethoxy)propyl]carbonate,(2-ethoxyethyl)[2-(2-butoxyethoxy)propyl]carbonate,(2-ethoxyethyl)[3-(2-methoxyethoxy)propyl]carbonate,(2-ethoxyethyl)[3-(2-ethoxyethoxy)propyl]carbonate,(2-ethoxyethyl)[3-(2-butoxyethoxy)propyl]carbonate,(2-ethoxyethyl)[4-(2-methoxyethoxy)butyl]carbonate,(2-ethoxyethyl)[4-(2-ethoxyethoxy)butyl]carbonate,(2-ethoxyethyl)[4-(2-butoxyethoxy)butyl]carbonate,(2-ethoxyethyl)[2-(2-methoxybutoxy)ethyl]carbonate,(2-ethoxyethyl)[2-(2-ethoxybutoxy)ethyl]carbonate,(2-ethoxyethyl)[2-(2-butoxybutoxy)ethyl]carbonate,(2-ethoxyethyl)[2-(2-methoxybutoxy)propyl]carbonate,(2-ethoxyethyl)[2-(2-ethoxybutoxy)propyl]carbonate,(2-ethoxyethyl)[3-(2-methoxybutoxy)propyl]carbonate,(2-ethoxyethyl)[3-(2-ethoxybutoxy)propyl]carbonate,(2-ethoxyethyl)[4-(2-methoxybutoxy)butyl]carbonate,(2-ethoxyethyl)[4-(2-ethoxybutoxy)butyl]carbonate, and(tetrahydrofurfuryl)[2-(2-methoxyethoxy)ethyl]carbonate.

Preferable among them are(methyl)[2-(2-(2-methoxyethoxy)ethoxy)ethyl]carbonate,(methyl)[2-(2-(2-ethoxyethoxy)ethoxy)ethyl]carbonate,(ethyl)[2-(2-(2-methoxyethoxy)ethoxy)ethyl]carbonate,(ethyl)[2-(2-(2-ethoxyethoxy)ethoxy)ethyl]carbonate,(2-methoxyethyl)[2-(2-methoxyethoxy)ethyl]carbonate,(2-methoxyethyl)[2-(2-ethoxyethoxy)ethyl]carbonate,(2-methoxyethyl)[2-(2-butoxyethoxy)ethyl]carbonate,(2-ethoxyethyl)[2-(2-methoxyethoxy)ethyl]carbonate,(2-ethoxyethyl)[2-(2-ethoxyethoxy)ethyl]carbonate, and(tetrahydrofurfuryl)[2-(2-methoxyethoxy)ethyl]carbonate.

Especially preferable among them are,(methyl)[2-(2-(2-methoxyethoxy)ethoxy)ethyl]carbonate,(methyl)[2-(2-(2-ethoxyethoxy)ethoxy)ethyl]carbonate,(ethyl)[2-(2-(2-methoxyethoxy)ethoxy)ethyl]carbonate,(ethyl)[2-(2-(2-ethoxyethoxy)ethoxy)ethyl]carbonate,(2-methoxyethyl)[2-(2-methoxyethoxy)ethyl]carbonate,(2-methoxyethyl)[2-(2-ethoxyethoxy)ethyl]carbonate,(2-ethoxyethyl)[2-(2-methoxyethoxy)ethyl]carbonate, and(2-ethoxyethyl)[2-(2-ethoxyethoxy)ethyl]carbonate.

(d) Carbonic esters having four ether linkages per molecule:

Examples of carbonic esters having four ether linkages per moleculeinclude bis[2-(2-methoxyethoxy)ethyl]carbonate,bis[2-(2-ethoxyethoxy)ethyl]carbonate,bis[2-(2-propoxyethoxy)ethyl]carbonate,(2-methoxyethyl)[2-(2-(2-methoxyethoxy)ethoxy)ethyl]carbonate,(2-ethoxyethyl)[2-(2-(2-methoxyethoxy)ethoxy)ethyl]carbonate,(2-butoxyethyl)[2-(2-(2-methoxyethoxy)ethoxy)ethyl]carbonate,(2-methoxyethyl)[2-(2-(2-ethoxyethoxy)ethoxy)ethyl]carbonate,(2-methoxyethyl)[2-(2-(2-butoxyethoxy)ethoxy)ethyl]carbonate,(2-ethoxyethyl)[2-(2-(2-butoxyethoxy)ethoxy)ethyl]carbonate,(2-butoxyethyl)[2-(2-(2-ethoxyethoxy)ethoxy)ethyl]carbonate,(methyl)[2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethyl]carbonate,(ethyl)[2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethyl]carbonate,(butyl)[2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethyl]carbonate,(butyl)[2-(2-(2-(2-ethoxyethoxy)ethoxy)ethoxy)ethyl]carbonate,(methyl)[2-(2-(2-(2-ethoxyethoxy)ethoxy)ethoxy)ethyl]carbonate,(methyl)[2-(2-(2-(2-butoxyethoxy)ethoxy)ethoxy)ethyl]carbonate, and(ethyl)[2-(2-(2-(2-butoxyethoxy)ethoxy)ethoxy)ethyl]carbonate.

Preferable among them are bis[2-(2-methoxyethoxy)ethyl]carbonate and(2-methoxyethyl)[2-(2-(2-methoxyethoxy)ethoxy)ethyl]carbonate.

(e) Carbonic esters having five ether linkages per molecule:

Examples of carbonic esters having five ether linkages per moleculeinclude(methyl)[2-(2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethoxy)ethyl]carbonate,(methyl)[2-(2-(2-(2-(2-ethoxyethoxy)ethoxy)ethoxy)ethoxy)ethyl]carbonate,(ethyl)[2-(2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethoxy)ethyl]carbonate,(ethyl)[2-(2-(2-(2-(2-ethoxyethoxy)ethoxy)ethoxy)ethoxy)ethyl]carbonate,(2-methoxyethyl)[2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethyl]carbonate,(2-methoxyethyl)[2-(2-(2-(2-ethoxyethoxy)ethoxy)ethoxy)ethyl]carbonate,(2-ethoxyethyl)[2-(2-(2-(2-ethoxyethoxy)ethoxy)ethoxy)ethyl]carbonate,[2-(2-methoxyethoxy)ethyl][2-(2-(2-methoxyethoxy)ethoxy)ethyl]carbonate,[2-(2-ethoxyethoxy)ethyl][2-(2-(2-methoxyethoxy)ethoxy)ethyl]carbonate,[2-(2-methoxyethoxy)ethyl][2-(2-(2-ethoxyethoxy)ethoxy)ethyl]carbonate,and[2-(2-ethoxyethoxy)ethyl][2-(2-(2-ethoxyethoxy)ethoxy)ethyl]carbonate.

(f) Carbonic esters having six ether linkages per molecule:

Examples of carbonic esters having six ether linkages per moleculeinclude bis[2-(2-(2-methoxyethoxy)ethoxy)ethyl]carbonate,bis[2-(2-(2-ethoxyethoxy)ethoxy)ethyl]carbonate, andbis[2-(2-(2-propoxyethoxy)ethoxy)ethyl]carbonate.

These compounds (Ia) may be used either any one singly or in combinationof any two or more at an arbitrary ratio.

The proportion of the compound (Ia) with respect to the non-aqueouselectrolyte solution (Ia) is usually 0.01 weight % or higher, preferably0.1 weight % or higher, especially preferably 0.3 weight % or higher,and usually 5 weight % or lower, preferably 4 weight % or lower,especially preferably 3 weight % or lower. If the proportion is toosmall, cycle characteristics at low temperature cannot be improved. Onthe other hand, if the proportion is too large, it is not preferablebecause battery characteristics after high-temperature storage tend todeteriorate. When two or more compounds (Ia) are combinedly used, thetotal proportion of the compounds (Ia) is required to satisfy the aboverange.

In the non-aqueous electrolyte solution (Ia), weight ratio between theunsaturated cyclic carbonate compound and the compound (Ia) (the weightof the unsaturated cyclic carbonate compound:the weight of the compound(Ia)) is within the range of usually 1:0.01 or higher, preferably 1:0.1or higher, and usually 1:50 or lower, preferably 1:10 or lower. If theratio of the compound (Ia) is too high, battery characteristics afterhigh-temperature storage tend to deteriorate, while if the ratio is toolow, cycle characteristics at low temperature cannot be improved. Whentwo or more unsaturated cyclic carbonate compounds and/or two or morecompounds (Ia) are combinedly used, the total proportion of theunsaturated cyclic carbonate compounds and/or the compounds (Ia) isrequired to satisfy the above range.

It is not clear why the non-aqueous electrolyte solution (Ia) containingthe unsaturated cyclic carbonate compound and the compound (Ia) canimprove cycle characteristics at low temperature, although the probablereason is presumed as follows.

Basically, an unsaturated cyclic carbonate compound such as vinylenecarbonate is reduced during initial charging and forms stable coating onthe negative electrode surface to thereby improve cycle characteristicsat room temperature. However, since lithium ion permeability of thecoating formed on the negative electrode surface fluctuates widelydepending on temperature, the lithium ion permeability at lowtemperature decreases drastically to bring about decrease in cyclecharacteristics at low temperature.

On the contrast, when the electrolyte solution contains the compound(Ia), complex coating originating in the unsaturated cyclic carbonatecompound and the compound (Ia) is formed on the negative electrodesurface. Since the complex coating is excellent in lithium ionpermeability even at low temperature, it is possible to keep excellentcycle characteristics at room temperature while achieving excellentcycle characteristics even at low temperature.

<Compound (Ib)>

The compound (Ib) is a compound expressed by the following generalformula (Ib).

In the general formula (Ib), R²¹ represents an alkyl group having 1-12carbon atoms or an alkenyl group having 2-12 carbon atoms. Betweenthese, the alkyl group is preferable.

Examples of the alkyl group are the ones whose number of carbon atoms isbetween 1-12, preferably 1-8, especially preferably 1-3, includingmethyl group, ethyl group, n-propyl group, i-propyl group, n-butylgroup, i-butyl group, sec-butyl group, tert-butyl group, pentyl group,cyclopentyl group, and cyclohexyl group. The alkyl group may be eitherchain or cyclic, between which the chain form is preferred.

Examples of the alkenyl group are the ones whose number of carbon atomsis between 2-12, preferably between 2-8, especially preferably between2-4, including vinyl group and propenyl group. The alkenyl group may beeither chain or cyclic, between which the chain form is preferred.

These alkyl groups and alkenyl groups may have one or more fluorineatoms that substitute for a part or all of the hydrogen atoms, and mayalso have one or more ether linkages within their chains.

The molecular weight of the compound (Ib) is usually 98 or larger andusually 650 or smaller, preferably 350 or smaller, more preferably 250or smaller. If the molecular weight is too large, solubility to theelectrolyte solution may decline significantly.

Examples of the compound (Ib) are methane sulfonyl fluoride, ethanesulfonyl fluoride, propane sulfonyl fluoride, 2-propane sulfonylfluoride, butane sulfonyl fluoride, 2-butane sulfonyl fluoride, hexanesulfonyl fluoride, octane sulfonyl fluoride, decane sulfonyl fluoride,dodecane sulfonyl fluoride, cyclohexane sulfonyl fluoride,trifluoromethane sulfonyl fluoride, perfluoroethane sulfonyl fluoride,perfluoropropane sulfonyl fluoride, perfluoro butane sulfonyl fluoride,ethene sulfonyl fluoride, 1-propene-1-sulfonyl fluoride,2-propene-1-sulfonyl fluoride, 2-methoxy-ethane sulfonyl fluoride, and2-ethoxy-ethane sulfonyl fluoride.

Preferable among them are methane sulfonyl fluoride, ethane sulfonylfluoride, propane sulfonyl fluoride, 2-propane sulfonyl fluoride, butanesulfonyl fluoride, and 2-butane sulfonyl fluoride, especially preferablebeing methane sulfonyl fluoride, ethane sulfonyl fluoride, and propanesulfonyl fluoride.

These compounds (Ib) may be used either any one singly or in combinationof any two or more at an arbitrary ratio.

The proportion of the compound (Ib) with respect to the non-aqueouselectrolyte solution (Ib) is usually 0.001 weight % or higher,preferably 0.05 weight % or higher, more preferably 0.1 weight % orhigher. If the concentration of the compound (Ib) is too low, scarcelyany effect can appear. However, on the other hand, if the concentrationof the compound (Ib) is too high, storage characteristics of the batterytends to decline. The upper limit is 5 weight % or lower, preferably 3weight % or lower, more preferably 1 weight % or lower. When two or morecompounds (Ib) are combinedly used, the total proportion of thecompounds (Ib) is required to satisfy the aforementioned range.

In the non-aqueous electrolyte solution (Ib), the weight ratio of thecompound (Ib) to the unsaturated cyclic carbonate compound (the weightof the compound (Ib):the weight of the unsaturated cyclic carbonatecompound) is usually 1:1 or higher, preferably 1:2 or higher, andusually 1:50 or lower, preferably 1:25 or lower. If the ratio of thecompound (Ib) is too high, battery characteristics afterhigh-temperature storage tends to decline, while if the ratio is toolow, gas generation during continuous charging cannot be inhibited. Whentwo or more unsaturated cyclic carbonate compounds and/or two or morecompounds (Ib) are combinedly used, the total proportion of theunsaturated cyclic carbonate compounds and/or the compounds (Ib) isrequired to satisfy the aforementioned range.

It is not clear why the non-aqueous electrolyte solution (Ib) containingboth the unsaturated cyclic carbonate compound and the compound (Ib)enables the resultant battery to keep high cycle characteristics whileimproving continuous charging characteristics and storagecharacteristics under high temperature and high voltage condition,although the probable reason is as follows.

During initial charging, complex coating is formed on the negativeelectrode surface from the unsaturated cyclic carbonate compound and thecompound (Ib), and on the positive electrode surface from the compound(Ib), in combination with other electrolyte solution components. Thecomplex coating is excellent in lithium ion permeability and stable evenat high temperature: supposedly the coating prevents the contact betweenthe electrodes with high activity and the electrolyte solution even inthe state of continuous charging or in the state of relatively hightemperature to suppress side reactions that may occur inside thebattery, thereby continuous charging characteristics and storagecharacteristics at high temperature being improved.

Also, since the unsaturated cyclic carbonate compound is prone to reactwith the positive electrode material in the state of charging, there isa problem that when the electrolyte solution contains the unsaturatedcyclic carbonate compound, the amount of gas generation duringcontinuous charging increases. However, it is assumed that when it isused in combination with the compound (Ib), the coating formed on thepositive electrode surface prevents the contact between the unsaturatedcyclic carbonate compound and the positive electrode to inhibit theamount of gas generation from increasing, whereby compatibility of cyclecharacteristics with battery characteristics at high temperature isrealized.

<Compound (Ic)>

The compound (Ic) is a compound expressed by the following generalformula (Ic).[Chemical Formula 11]CF_(n)H_((3-n))CH₂X³  (Ic)(in the formula (Ic), n represents an integer of between 1-3, and X³represents a group selected from the groups expressed by the followingformulae (Ic-1)-(Ic-4).

in the formulae (Ic-1)-(Ic-4), R³¹-R³⁴ represent, independently of eachother, an alkyl group having 1-20 carbon atoms that may be substitutedby a halogen atom, Y³ represents a divalent hydrocarbon group having1-10 carbon atoms that may be substituted by a halogen atom.)

In the formulae, R³¹-R³⁴ each represent a straight-chain, branched-chainor cyclic alkyl group having 1-20 carbon atoms that may be substitutedby a halogen atom. The number of carbon atoms is within the range ofusually 1 or more, preferably 2 or more, and usually 20 or less,preferably 10 or less, more preferably 6 or less.

Examples of R³¹-R³⁴ are methyl group, ethyl group, n-propyl group,i-propyl group, n-butyl group, i-butyl group, sec-butyl group,tert-butyl group, pentyl group, cyclopentyl group, hexyl group,cyclohexyl group, octyl group, decyl group, and dodecyl group.

R³¹-R³⁴ may be substituted by a halogen atom. The halogen atom is notparticularly limited in its kind, although it is preferable in terms ofelectrochemical stability to be a fluorine atom or a chlorine atom,especially preferably a fluorine atom. The number of substituent halogenatoms is not particularly limited, although being usually 20 or less,preferably 12 or less.

Examples of alkyl groups substituted by halogen atoms are:

fluoromethyl group, difluoromethyl group, trifluoromethyl group;

1-fluoroethyl group, 2-fluoroethyl group, 1,1-difluoroethyl group,1,2-difluoroethyl group, 2,2-difluoroethyl group, 1,1,2-trifluoroethylgroup, 1,2,2-trifluoroethyl group, 2,2,2-trifluoroethyl group,1,1,2,2-tetrafluoroethyl group, 1,2,2,2-tetrafluoroethyl group,pentafluoroethyl group;

1-fluoropropyl group, 2-fluoropropyl group, 3-fluoropropyl group,1,1-difluoropropyl group, 1,2-difluoropropyl group, 1,3-difluoropropylgroup, 2,2-difluoropropyl group, 2,3-difluoropropyl group,3,3-difluoropropyl group, 1,1,2-trifluoropropyl group,1,1,3-trifluoropropyl group, 1,2,2-trifluoropropyl group,1,2,3-trifluoropropyl group, 1,3,3-trifluoropropyl group,2,2,2-trifluoropropyl group, 2,2,3-trifluoropropyl group,2,3,3-trifluoropropyl group, 3,3,3-trifluoropropyl group,1,1,2,2-tetrafluoropropyl group, 1,1,2,3-tetrafluoropropyl group,1,1,3,3-tetrafluoropropyl group, 1,2,2,3-tetrafluoropropyl group,1,2,3,3-tetrafluoropropyl group, 1,3,3,3-tetrafluoropropyl group,2,3,3,3-tetrafluoropropyl group, 1,1,2,2,3-pentafluoropropyl group,1,1,2,3,3-pentafluoropropyl group, 1,1,3,3,3-pentafluoropropyl group,1,2,2,3,3-pentafluoropropyl group, 1,2,3,3,3-pentafluoropropyl group,2,2,3,3,3-pentafluoropropyl group, 1,1,2,2,3,3-hexafluoropropyl group,1,1,2,3,3,3-hexafluoropropyl group, 1,2,2,3,3,3-hexafluoropropyl group,heptafluoropropyl group;

1-fluoro butyl group, 2-fluoro butyl group, 3-fluoro butyl group,4-fluoro butyl group, 1,1-difluoro butyl group, 1,2-difluoro butylgroup, 1,3-difluoro butyl group, 1,4-difluoro butyl group, 2,2-difluorobutyl group, 2,3-difluoro butyl group, 2,4-difluoro butyl group,3,3-difluoro butyl group, 3,4-difluoro butyl group, 4,4-difluoro butylgroup, 1,1,2-trifluoro butyl group, 1,1,3-trifluoro butyl group,1,1,4-trifluoro butyl group, 1,2,2-trifluoro butyl group,1,2,3-trifluoro butyl group, 1,2,4-trifluoro butyl group,1,3,3-trifluoro butyl group, 1,3,4-trifluoro butyl group,1,4,4-trifluoro butyl group, 2,2,3-trifluoro butyl group,2,2,4-trifluoro butyl group, 2,3,3-trifluoro butyl group,2,3,4-trifluoro butyl group, 2,4,4-trifluoro butyl group,3,3,4-trifluoro butyl group, 3,4,4-trifluoro butyl group,4,4,4-trifluoro butyl group;

1-fluoropentyl group, 2-fluoropentyl group, 3-fluoropentyl group,4-fluoropentyl group, 5-fluoropentyl group, 1,1-difluoropentyl group,1,2-difluoropentyl group, 1,3-difluoropentyl group, 1,4-difluoropentylgroup, 1,5-difluoropentyl group, 2,2-difluoropentyl group,2,3-difluoropentyl group, 2,4-difluoropentyl group, 2,5-difluoropentylgroup, 3,3-difluoropentyl group, 3,4-difluoropentyl group,3,5-difluoropentyl group, 4,4-difluoropentyl group, 4,5-difluoropentylgroup, 5,5-difluoropentyl group, 1,1,2-trifluoropentyl group,1,1,3-trifluoropentyl group, 1,1,4-trifluoropentyl group,1,1,5-trifluoropentyl group, 1,2,2-trifluoropentyl group,1,2,3-trifluoropentyl group, 1,2,4-trifluoropentyl group,1,2,5-trifluoropentyl group, 1,3,3-trifluoropentyl group,1,3,4-trifluoropentyl group, 1,3,5-trifluoropentyl group,1,4,4-trifluoropentyl group, 1,4,5-trifluoropentyl group,1,5,5-trifluoropentyl group, 2,2,2-trifluoropentyl group,2,2,3-trifluoropentyl group, 2,2,4-trifluoropentyl group,2,2,5-trifluoropentyl group, 2,3,3-trifluoropentyl group,2,3,4-trifluoropentyl group, 2,3,5-trifluoropentyl group,2,4,4-trifluoropentyl group, 2,4,5-trifluoropentyl group,2,5,5-trifluoropentyl group, 3,3,3-trifluoropentyl group,3,3,4-trifluoropentyl group, 3,3,5-trifluoropentyl group,3,4,4-trifluoropentyl group, 3,4,5-trifluoropentyl group,3,5,5-trifluoropentyl group, 4,4,4-trifluoropentyl group,4,4,5-trifluoropentyl group, 4,5,5-trifluoropentyl group,5,5,5-trifluoropentyl group;

1-fluorohexyl group, 1,1-difluorohexyl group, and 1,1,2-trifluorohexylgroup.

It is particularly preferable that R³¹-R³⁴ in the formulae (Ic-1)-(Ic-4)each are an alkyl group having 1-20 carbon atoms substituted by 1-3fluorine atoms. Specifically, the compound (Ic) is preferable to havefluorine atoms at its both ends.

Y³ in the formula (Ic-2) represents a divalent hydrocarbon group having1-10 carbon atoms that may be substituted by a halogen atom. The numberof carbon atoms is within the range of usually 1 or more, preferably 2or more, and usually 6 or less, preferably 4 or less. Its examplesinclude divalent hydrocarbon groups such as alkylene groups and arylenegroups, which are obtained by removing two hydrogen atoms from alkanes,such as methane, ethane, propane, n-butane, isobutane, n-pentane,isopentane, and neopentane, and aromatic hydrocarbons, such as benzene,toluene, and xylene. Preferable are alkylene groups.

These hydrocarbon groups may be substituted further with a halogen atom.The halogen atom is not particularly limited in its kind, although interms of electrochemical stability it is preferable to be a fluorineatom or a chlorine atom, between which a fluorine atom is preferred. Thenumber of substituent halogen atoms is not particularly limited,although being usually 20 or less, preferably 12 or less.

The molecular weight of the compound (Ic) is usually 70 or greater,preferably 90 or greater, and usually 1000 or smaller, preferably 500 orsmaller. The molecular weight equaling or exceeding the aforementionedlower limit is indispensable in order to satisfy the structure of thegeneral formula (Ic). On the other hand, if it exceeds the upper limit,the compound molecules may not cluster densely when coating is formed onthe negative electrode surface and that anticipated characteristicstherefore may not be obtained.

Examples of the compound (Ic) are mentioned below, although the compoundis not limited in its kind to the following examples but may be anycompound unless it runs counter to the gist of the present invention.

Compounds in which X³ is expressed by general formula (Ic-1) (monoethercompounds):CFH₂CH₂OCH₂CH₃  (1)CFH₂CH₂OCH₂CH₂F  (2)CF₂HCH₂OCH₂CH₃  (3)CF₂HCH₂OCH₂CHF₂  (4)CF₃CH₂OCH₂CH₃  (5)CF₃CH₂OCH₂CF₃  (6)

Compounds in which X³ is expressed by general formula (Ic-2) (diethercompounds):CFH₂CH₂OCH₂CH₂OCH₂CH₃  (7)CFH₂CH₂OCH₂CH₂OCH₂CH₂F  (8)CF₂HCH₂OCH₂CH₂OCH₂CH₃  (9)CF₂HCH₂OCH₂CH₂OCH₂CHF₂  (10)CF₃CH₂OCH₂CH₂OCH₂CH₃  (11)CF₃CH₂OCH₂CH₂OCH₂CF₃  (12)

Compounds in which X³ is expressed by general formula (Ic-3) (estercompounds):CFH₂CH₂OC(═O)CH₃  (13)CFH₂CH₂OC(═O)CFH₂  (14)CF₂HCH₂OC(═O)CH₃  (15)CF₂HCF₂OC(═O)CF₂H  (16)CF₃CH₂OC(═O)CH₃  (17)CF₃CH₂OC(═O)CF₃  (18)

Compounds in which X³ is expressed by general formula (Ic-4) (carbonatecompounds):CFH₂CH₂OC(═O)OCH₂CH₃  (19)CFH₂CH₂OC(═O)OCH₂CH₂F  (20)CF₂HCH₂OC(═O)OCH₂CH₃  (21)CF₂HCH₂OC(═O)OCH₂CHF₂  (22)CF₃CH₂OC(═O)OCH₂CH₃  (23)CF₃CH₂OC(═O)OCH₂CF₃  (24)

In the non-aqueous electrolyte solution (Ic), the compound (Ic) may beused either any one singly or in combination of any two or more in anyproportion.

The concentration of the compound (Ic) in the non-aqueous electrolytesolution (Ic) is within the range of usually 0.01 weight % or higher,preferably 0.05 weight % or higher, especially preferably 0.1 weight %or higher, and usually 5 weight % or lower, preferably 4 weight % orlower, more preferably 3 weight % or lower, especially preferably 2weight % or lower. If the content of the compound (Ic) is too low,inhibitory effect of degradation under high voltage may not appear to anadequate degree. On the other hand, if the proportion is too high,characteristics such as large-current characteristics of the battery maytend to decline. When two or more compounds (Ic) are combinedly used,the total proportion of the compounds (Ic) is required to meet theaforementioned range.

In the non-aqueous electrolyte solution (Ic) the weight ratio betweenthe unsaturated cyclic carbonate compound and the compound (Ic) (theweight of the unsaturated cyclic carbonate compound/the weight of thecompound (Ic)) is within the range of usually 0.001 or higher,preferably 0.01 or higher, especially preferably 0.05 or higher, andusually 1000 or lower, preferably 100 or lower. If the ratio of thecompound (Ic) is too high, battery characteristics afterhigh-temperature storage tend to decline. If the ratio is too low, gasgeneration during continuous charging cannot be suppressed. When two ormore unsaturated cyclic carbonate compounds and/or two or more compounds(Ic) are combinedly used, the total proportion of the unsaturated cycliccarbonate compounds and/or the compounds (Ic) is required to meet theaforementioned range.

It is not clear why the use of the non-aqueous electrolyte solution (Ic)containing both the unsaturated cyclic carbonate compound and thecompound (Ic) in a secondary battery, especially in a lithium secondarybattery, can inhibit degradation when used high voltage, althoughsupposedly the reason is as follows.

In the non-aqueous electrolyte solution (Ic), the unsaturated cycliccarbonate compound forms good coating on the negative electrode.However, since the unsaturated cyclic carbonate compound is vulnerableto oxidation, the battery may be adversely affected in itscharacteristics when used under high voltage. On the other hand, thefluorine-containing compound also forms coating, although it produces anexcessive amount of coating under high voltage to bring aboutdeterioration in battery characteristics. Thus, the unsaturated cycliccarbonate compound and the fluorine-containing compound have theirrespective advantages and drawbacks. However, when the unsaturatedcyclic carbonate compound is used in combination with the compound (Ic)being a fluorine-containing compound, it is supposed that the coatingformed by the compound (Ic) inhibits the unsaturated cyclic carbonatecompound from being oxidized while the coating formed by the unsaturatedcyclic carbonate compound inhibits compound (Ic) from decomposed.According to the present invention, since the unsaturated cycliccarbonate compound is used in combination with the compound (Ic) being afluorine-containing compound in combination, these compounds can thusact complementarily to each other to thereby produce tolerance for useunder high voltage.

In view of achieving the aforementioned effects, if the concentration ofthe compound (Ic) in the non-aqueous electrolyte solution (Ic) is toolow, coating may not be formed adequately to produce the effects. On theother hand, if the concentration is too high, the coating may be formedexcessively and denatured, exerting a detrimental effect on batterycharacteristics. The same is applied to the concentration of theunsaturated cyclic carbonate compound in the non-aqueous electrolytesolution (Ic): if the concentration is too high, an excessive amount ofnegative electrode coating may be formed to impede the travel of lithiumions, while if the concentration is too low, only an inadequate amountof negative electrode coating may be formed to cause degradation. Forthis reason, the concentration range defined in the present invention isconsidered to be most favorable.

<Others>

When the non-aqueous electrolyte solution (I) contains two or more ofthe compound (Ia), the compound (Ib), and the compound (Ic), the totalconcentration of compounds (I) with respect to the non-aqueouselectrolyte solution (I) is within the range of usually 0.01 weight % orhigher, preferably 0.05 weight % or higher, especially preferably 0.1weight % or higher, and usually 5 weight % or lower, preferably 4 weight% or lower, more preferably 3 weight % or lower. If the content of thecompounds (I) is too low, inhibitory effect of degradation under highvoltage may not appear to an adequate extent. On the other hand, if theproportion is too high, characteristics such as large-currentcharacteristics of the battery tend to decline.

When the non-aqueous electrolyte solution (I) contains two or more ofthe compound (Ia), the compound (Ib), and the compound (Ic), the weightratio between the unsaturated cyclic carbonate compound and the total ofthe compounds (I) in the non-aqueous electrolyte solution (I) (theweight of the unsaturated cyclic carbonate compound/the total weight ofthe compounds (I)) is within the range of usually 0.001 or higher,preferably 0.01 or higher, especially preferably 0.05 or higher, andusually 1000 or lower, preferably 100 or lower. If the ratio of thecompounds (I) is too high, battery characteristics afterhigh-temperature storage tend to deteriorate. If the ratio is too low,it is possible neither to improve cycle characteristics at lowtemperature nor to inhibit gas generation during continuous charging.

[Other Ingredients]

In addition to the aforementioned electrolyte, non-aqueous solvent,unsaturated cyclic carbonate compound (A ingredient), and compound (I)(B ingredient), the non-aqueous electrolyte solution of the presentinvention (I) may contain one or more other ingredients in such anamount as not to impair the effects of the present invention. Examplesof other ingredients are conventionally known various assistants, suchas anti-overcharging agents, acid removers, dehydrators, and fireretardants.

Among such assistants, examples of anti-overcharging agents are:aromatic compounds such as biphenyl, alkyl biphenyl, terphenyl,partially-hydrogenation products of terphenyl, cyclohexyl benzene,t-butyl benzene, t-amyl benzene, diphenyl ether, and dibenzofuran, etc.;partially fluorination products of the aforementioned aromaticcompounds, such as 2-fluoro biphenyl, o-cyclohexyl fluoro benzene, andp-cyclohexyl fluoro benzene; fluorine-containing anisole compounds suchas 2,4-difluoro anisole, 2,5-difluoro anisole, and 2,6-difluoro anisole.These may be used either any one singly or in combination of two or moreat an arbitrary ratio. Containing these anti-overcharging agents at aconcentration equal to or higher than the lower limit value enables toinhibit a rupture or ignition of the battery even in such a case ofovercharging. If their concentration exceeds the upper limit value, theymay react during high-temperature storage in the regions of theelectrodes that exhibit relatively high activity. Reactions of thesecompounds may bring about marked decrease in discharging characteristicsafter continuous charging and discharging characteristics afterhigh-temperature storage due to marked increase in internal resistanceof the battery or gas generation.

Examples of other assistants are: carbonate compounds such asfluoroethylene carbonate, trifluoropropylene carbonate, phenyl ethylenecarbonate, erythritan carbonate, and spiro-bis-dimethylene carbonate;carboxylic anhydrides such as succinic anhydride, glutaric anhydride,maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconicanhydride, diglycolic anhydride, cyclohexane dicarboxylic anhydride,cyclopentane tetracarboxylic dianhydride and phenyl succinic anhydride;sulfur-containing compounds such as ethylene sulfite, 1,3-propanesultone, 1,4-butane sultone, methyl methanesulfonate, busulfan,sulfolane, sulfolene, dimethyl sulfone, tetramethyl thiuram monosulfide,N,N-dimethyl methane sulfone amide, and N,N-diethyl methane sulfoneamide; nitrogen-containing compounds such as 1-methyl-2-pyrrolidinone,1-methyl-2-piperidone, 3-methyl-2-oxazolidinone,1,3-dimethyl-2-imidazolidinone, and N-methyl succinimide; hydrocarboncompounds such as heptane, octane, and cycloheptane; fluorine-containingaromatic compounds such as fluoro benzene, difluoro benzene, hexafluorobenzene, and benzotrifluoride; and phosphorus-containing compounds suchas trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate,methyl diethyl phosphate, ethylene methyl phosphate, ethylene ethylphosphate, and tris(trifluoroethyl)phosphate. These may be used eitherany one singly or in combination of two or more at an arbitrary ratio.

When the non-aqueous electrolyte solution of the present invention (I)contains these assistants, their content with respect to the non-aqueouselectrolyte solution is within the range of usually 0.01 weight % orhigher and usually 5 weight % or lower. Contained in the non-aqueouselectrolyte solution of the present invention, these assistants canimprove capacity-maintenance characteristics after high-temperaturestorage and cycle characteristics.

[Production Method of Non-Aqueous Electrolyte Solution (I)]

The non-aqueous electrolyte solution of the present invention (I) can beprepared by dissolving in the aforementioned non-aqueous solvent theaforementioned electrolyte, unsaturated cyclic carbonate compound (Aingredient), and compound (I) (B ingredient), together with otherassistants, which are used according to need. Before preparing thenon-aqueous electrolyte solution (I), it is desired to dewater eachingredient such as the non-aqueous solvent in advance. Specifically, itis desirable to carry out dewatering until its water content becomesusually 50 ppm or lower, preferably 30 ppm or lower. The methods ofdewatering can be selected arbitrarily, examples of which methods areheating under a reduced pressure or passing through a molecular sieve.

The non-aqueous electrolyte solution of the present invention (I) mayalso be prepared in a semisolid state through gelation using agelatinizer such as macromolecules. The ratio of the non-aqueouselectrolyte solution (I) in the semisolid electrolyte is within therange of usually 30 weight % or higher, preferably 50 weight % orhigher, more preferably 75 weight % or higher, and usually 99.95 weight% or lower, preferably 99 weight % or lower, more preferably 98 weight %or lower with respect to the total weight of the semisolid electrolyte.If the ratio of the non-aqueous electrolyte solution (I) is too high,the non-aqueous electrolyte solution (I) may hardly be secured and istherefore prone to cause leakage. On the other hand, if the ratio of thenon-aqueous electrolyte solution (I) is too low, the battery may bedeficient in charge and discharge efficiencies and capacity.

[2: Non-Aqueous Electrolyte Solution (II)]

The non-aqueous electrolyte solution according to the second aspect ofthe present invention (hereinafter also called “non-aqueous electrolytesolution (II)”) contains a lithium salt and a non-aqueous solvent, andis characterized in that it further contains a compound (II)(hereinafter also called “C ingredient”) that is described later.Besides, it is preferable to contain a cyclic carbonate compound havingan unsaturated bond (hereinafter also called “D ingredient”).

[Electrolyte]

The electrolyte used in the non-aqueous electrolyte solution (II) is notparticularly limited and can be selected arbitrarily from knownsubstances used as an electrolyte of a secondary battery. As regards alithium secondary battery, a lithium salt is usually used as theelectrolyte. The details of the lithium salt, such as its selections andits amount of usage, are the same as explained above in connection withthe non-aqueous electrolyte solution (I).

[Non-Aqueous Solvent]

As the non-aqueous solvent of the non-aqueous electrolyte solution (II),it is possible to use any substance conventionally known as solvents fornon-aqueous electrolyte solutions, although an organic solvent isusually selected. The details of the organic solvent, such as itsselections and its amount of usage, the non-aqueous electrolyte solution(I), are the same as explained above in connection with the non-aqueouselectrolyte solution (I).

[Compound (II) (C Ingredient)]

The non-aqueous electrolyte solution (II) contains, as C ingredient, atleast one compound of a compound (IIa), a compound (IIb), and a compound(IIc) (hereinafter also called “compound (II)”). The non-aqueouselectrolyte solution (II) may contain any one of the compound (IIa), thecompound (IIb), and the compound (IIc) singly, or may contain two orthree of them in combination. In the following description, thenon-aqueous electrolyte solutions (II) that each contain a respectiveone of the compound (IIa), the compound (IIb), the compound (IIc) willbe respectively called the “non-aqueous electrolyte solution (IIa)”through the “non-aqueous electrolyte solution (IIc)” when explainedseparately, while they will be collectively called the “non-aqueouselectrolyte solution (II)” when explained without particulardistinction.

<Compound (IIa)>

The compound (IIa) is a compound having a structure expressed by thefollowing general formula (IIa).

Among the compounds (IIa), preferred is a compound expressed by thefollowing general formula (IIa′) (hereinafter also called “compound(IIa)'”).

(in the formula (IIa′), R⁴¹-R⁴⁴ represent, independently of each other,a hydrogen atom, an alkyl group having 1-12 carbon atoms that may besubstituted by a fluorine atom, an alkenyl group having 2-12 carbonatoms that may be substituted by a fluorine atom, an aryl group having6-12 carbon atoms that may be substituted by a fluorine atom, or anaralkyl group having 7-12 carbon atoms that may be substituted by afluorine atom. The group may have an ether linkage in its chain. R⁴¹ maybe linked with R⁴², and R⁴³ may be linked with R⁴⁴, to form a ring thatmay have an oxygen atom.)

In the general formula (IIa′), R⁴¹-R⁴⁴ represent, independently of eachother, a hydrogen atom, an alkyl group having 1-12 carbon atoms, analkenyl group having 2-12 carbon atoms, an aryl group having 6-12 carbonatoms, or an aralkyl group having 7-12 carbon atoms.

The alkyl group, alkenyl group, aryl group, or aralkyl group may haveone or more fluorine atoms that substitute a part or all of the hydrogenatoms, and may also have an ether linkage in its chain.

Examples of alkyl groups are the ones whose number of carbon atoms isbetween 1-12, preferably between 1-8, such as methyl group, ethyl group,n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butylgroup, tert-butyl group, pentyl group, cyclopentyl group, cyclohexyl,etc.

Examples of alkenyl groups are the ones whose number of carbon atoms isbetween 1-12, preferably between 2-8, especially preferably between 2-4,such as vinyl group and propenyl group.

Examples of aryl groups include phenyl group, tolyl group, and xylylgroup, among which phenyl group is preferred.

Examples of aralkyl group include benzyl group and phenethyl group.

R⁴¹ may be coupled with R⁴², and R⁴³ may be coupled with R⁴⁴, to form acyclic structure that may contain an oxygen atom, e.g., a cycloalkanestructure having 3-12 carbon atoms.

Among these, it is preferable that R⁴¹-R⁴⁴ is, independently of eachother: a hydrogen atom, an alkyl group having 1-12 carbon atoms that maybe substituted by a fluorine atom; or an alkenyl group having 2-12carbon atoms that may be substituted by a fluorine atom.

The molecular weight of the compound (IIa′) is usually 160 or larger andusually 900 or smaller, preferably 650 or smaller. If the molecularweight is too large, its solubility in the electrolyte solutiondecreases markedly.

Examples of the compound (IIa′) can be mentioned as follows.

As the compound in which each of R⁴¹-R⁴⁴ is a hydrogen atom,2,4,8,10-tetraoxaspiro[5.5]undecane can be mentioned.

As the compounds in which any of R⁴¹-R⁴⁴ is an alkyl group, there can bementioned 3,9-dimethyl-2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-diethyl-2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-dipropyl-2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-dioctyl-2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-didecyl-2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-diundecyl-2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-didodecyl-2,4,8,10-tetraoxaspiro[5.5]undecane,3,3,9,9-tetramethyl-2,4,8,10-tetraoxaspiro[5.5]undecane,3,3,9,9-tetraethyl-2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-diethyl-3,9-dimethyl-2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-dicyclohexyl-2,4,8,10-tetraoxaspiro[5.5]undecane, etc.

As the compounds in which any of R⁴¹-R⁴⁴ is an alkenyl group, there canbe mentioned 3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-di-1-propenyl-2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-di-2-propenyl-2,4,8,10-tetraoxaspiro[5.5]undecane, etc.

As the compounds in which any of R⁴¹-R⁴⁴ is an aryl group, there can bementioned 3,9-diphenyl-2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-bis(4-fluoro phenyl)-2,4,8,10-tetraoxaspiro[5.5]undecane, etc.

As the compounds in which either R⁴¹ is coupled with R⁴², or R⁴³ iscoupled with R⁴⁴, to form a cyclic structure, there can be mentioned7,11,18,21-tetraoxatrispiro[5.2.2.5.2.2]heneicosane,6,10,16,19-tetraoxatrispiro[4.2.2.4.2.2]nonadecane, etc.

As the compounds in which any of R⁴¹-R⁴⁴ has an ether linkage in itschain, there can be mentioned3,9-dimethoxy-2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-diethoxy-2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-bis(methoxymethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-bis(2-methoxyethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-bis(2-ethoxyethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane, etc.

Among these, preferred are 2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-dimethyl-2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-diethyl-2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-dipropyl-2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-di-1-propenyl-2,4,8,10-tetraoxaspiro[5.5]undecane, and3,9-di-2-propenyl-2,4,8,10-tetraoxaspiro[5.5]undecane, especiallypreferred being 2,4,8,10-tetraoxaspiro[5.5]undecane and3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane.

For the non-aqueous electrolyte solution (IIa), the compounds (IIa) maybe used either any one singly or in combination of any two or more at anarbitrary proportion.

The proportion of compound (IIa) in the non-aqueous electrolyte solution(IIa) is usually 0.001 weight % or higher. If its concentration is lowerthan the limit, it scarcely exhibits any effect. The concentration ispreferably 0.05 weight % or higher, especially preferably 0.1 weight %or higher. On the other hand, if the concentration is too high, storagecharacteristics of the battery tend to decline. The upper limit isusually 10 weight % or lower, preferably weight % or lower, morepreferably 4 weight % or lower. In view of relationship of theconcentration with various characteristics of the electrolyte solution,the concentration is preferably 3 weight % or lower, further preferably2 weight % or lower, still further preferably 1 weight % or lower. Whentwo or more compounds (IIa) are combinedly used, the total proportion ofthe compounds (IIa) is required to meet the aforementioned range.

It is not clear why the non-aqueous electrolyte solution (IIa)containing the compound (IIa) improves continuous chargingcharacteristics, although the probable reason is presumed as follows.Basically, the compound (IIa) causes reactions on the negative electrodeand positive electrode surfaces during initial charging, forms complexcoating together with ingredients of the electrolyte solution. Aspresumed from the structure expressed by the formula (IIa), the complexcoating contains a lot of oxygen atoms that are located in appropriatepositions, which may bring about both excellent lithium ion permeabilityand stability at high temperature. Presumably the coating prevents thecontact between the electrodes with high activity and the electrolytesolution even in the state of continuous charging or in the state ofrelatively high temperature, as results of which it becomes possible toinhibit side reactions inside the battery and to improve continuouscharging characteristics.

On the other hand, when using cyclic ether compounds whose structuresfall outside the definition of the formula (IIa), such as dioxolane,tetrahydrofuran, tetrahydropyran, and dioxane, battery characteristicstend to decline presumably because the resultant complex coating isinferior in lithium ion permeability and unstable at high temperature.

<Compound (IIb)>

The compound (IIb) is a compound expressed by the following generalformula (IIb).

In the formula (IIb), Z⁵ represents an integer of 2 or larger andusually 8 or smaller, preferably 4 or smaller. It is especiallypreferable that Z⁵=2.

X⁵ represents a Z-valent linkage group composed of one or more atomsselected from the group consisting of a carbon atom, a hydrogen atom, afluorine atom and an oxygen atom, and the fluoro sulfonyl group is boundto a carbon atom of the linkage group. Examples of the linkage group arehydrocarbon groups and fluorine-substituted hydrocarbon groups, as wellas the hydrocarbon groups whose chains contain any linkage such as etherlinkage or ester linkage. Examples of the hydrocarbon group arealiphatic hydrocarbon groups, such as saturated aliphatic hydrocarbongroups and unsaturated aliphatic hydrocarbon groups, as well as aromatichydrocarbon groups. Among these aliphatic hydrocarbon groups arepreferred, especially preferable being saturated aliphatic hydrocarbongroups. The aliphatic hydrocarbon groups may be either chain or cyclic,although chain is preferred. These hydrocarbon groups may have one ormore fluorine atoms substituting a part or all of the hydrogen atoms.The number of carbon atoms of the linkage group is usually between 1-12,preferably between 2-8.

Examples of the linkage groups where Z⁵=2 are enumerated below.

Examples of the linkage groups where Z⁵=3 are enumerated below.

Examples of the linkage groups where Z⁵=4 are enumerated below.

The molecular weight of the compound (IIb) is usually 180 or larger andusually 1000 or smaller, preferably 650 or smaller, more preferably 350or smaller. If the molecular weight is too large, solubility in theelectrolyte solution may decrease markedly.

Examples of the compounds (IIb) where Z⁵=2 are methane-bis(sulfonylfluoride), ethane-1,2-bis(sulfonyl fluoride), propane-1,3-bis(sulfonylfluoride), propane-1,2-bis(sulfonyl fluoride), butane-1,4-bis(sulfonylfluoride), butane-1,2-bis(sulfonyl fluoride), butane-1,3-bis(sulfonylfluoride), difluoromethane bis(sulfonyl fluoride),1,1,2,2-tetrafluoroethane-1,2-bis(sulfonyl fluoride),1,1,2,2,3,3-hexafluoropropane-1,3-bis(sulfonyl fluoride),1,1,2,2,3,3,4,4-octafluoro butane-1,4-bis(sulfonyl fluoride),2,2′-oxybis(ethane sulfonyl fluoride),2,2′-oxybis(1,1,2,2-tetrafluoroethane sulfonyl fluoride), etc.

Examples of the compounds (IIb) where Z⁵=3 arepropane-1,2,3-tris(sulfonyl fluoride), butane-1,2,3-tris(sulfonylfluoride), butane-1,2,4-tris(sulfonyl fluoride),1,1,2,3,3-pentafluoropropane-1,2,3-tris(sulfonyl fluoride), etc.

Examples of the compounds (IIb) where Z⁵=4 arebutane-1,2,3,4-tetrakis(sulfonyl fluoride),1,1,2,3,4,4-hexafluorobutane-1,2,3,4-tetrakis(sulfonyl fluoride), etc.

Preferable among these are methane-bis(sulfonyl fluoride),ethane-1,2-bis(sulfonyl fluoride), propane-1,3-bis(sulfonyl fluoride),propane-1,2-bis(sulfonyl fluoride), butane-1,4-bis(sulfonyl fluoride),difluoromethane bis(sulfonyl fluoride),1,1,2,2-tetrafluoroethane-1,2-bis(sulfonyl fluoride),1,1,2,2,3,3-hexafluoropropane-1,3-bis(sulfonyl fluoride),1,1,2,2,3,3,4,4-octafluoro butane-1,4-bis(sulfonyl fluoride), andpropane-1,2,3-tris(sulfonyl fluoride).

More preferably, ethane-1,2-bis(sulfonyl fluoride),propane-1,3-bis(sulfonyl fluoride), butane-1,4-bis(sulfonyl fluoride),1,1,2,2-tetrafluoroethane-1,2-bis(sulfonyl fluoride),1,1,2,2,3,3-hexafluoropropane-1,3-bis(sulfonyl fluoride), and1,1,2,2,3,3,4,4-octafluoro butane-1,4-bis(sulfonyl fluoride) arementioned.

In the non-aqueous electrolyte solution (IIb), the compounds (IIb) maybe used either any one singly or in combination of any two or more inany ratio.

The proportion of the compound (IIb) in the non-aqueous electrolytesolution (IIb) is usually 0.001 weight % or higher. If the concentrationof the compound (IIb) is lower than the limit, it exhibits scarcely anyeffects. It is preferably 0.05 weight % or higher, especially preferably0.1 weight % or higher. However, if the concentration is too high,storage characteristics of the battery tend to decline. There is hencean upper limit of usually 5 weight % or lower, preferably 3 weight % orlower, more preferably 1 weight % or lower. When two or more compounds(IIb) are combinedly used, the total proportion of the compounds (IIb)is required to meet the aforementioned range.

It is not clear why the non-aqueous electrolyte solution containing thecompound (IIb) improves the battery characteristics underhigh-temperature, high-voltage condition such as continuous chargingcharacteristics and storage characteristics, although the probablereason is presumed as following. Basically, the compound (IIb) causesreactions on the negative electrode and positive electrode surfacesduring initial charging and forms complex coating together with otherelectrolyte solution ingredients. Since the complex coating exhibitsexcellent lithium ion permeability and is stable even at hightemperature, it is presumed that even in the state of continuouscharging or in the state of relatively high temperature, the coatingprevents the contact between the electrodes with high activity and theelectrolyte solution to thereby suppress side reactions that may occurinside the battery.

On the other hand, a compound having a single fluoro sulfonyl group,such as benzene sulfonyl fluoride and p-toluene sulfonyl fluoride, mayform complex coating that is inferior in lithium ion permeability andunstable at high temperature. It is presumably because the resultantbattery increases its internal resistance when stored underhigh-temperature condition, bringing about deterioration in batterycharacteristics such as storage characteristics at high temperature andcontinuous charging characteristics.

<Compound (IIc)>

The compound (IIc) is a compound expressed by the following generalformula (IIc).

In the formula (IIc), Z⁶ represents an integer of 2 or larger. Althoughnot being restricted, the upper limit is preferably 4 or smaller, morepreferably 3 or smaller. Especially preferred is that Z⁶=2. If Z⁶ issmaller than two, discharging storage characteristics may deteriorate.

R⁶¹ represent, independently of each other, an alkyl group. The numberof carbon atoms is within the range of usually 1 or more and usually 6or less, preferably 4 or less. Examples of alkyl groups for R⁶¹ aremethyl group, ethyl group, n-propyl group, i-propyl group, n-butylgroup, i-butyl group, sec-butyl group, tert-butyl group, pentyl group,cyclopentyl group, and cyclohexyl group. These alkyl groups may besubstituted by other groups. The substituents that the alkyl groups ofR⁶¹ may have are not particularly limited unless they depart from thegist of the non-aqueous electrolyte solution of the present invention,although halogen atoms, alkoxy groups, hydroxy groups, and amino groupsare desirable. Z⁶ alkyl groups of R⁶¹, including their substituents ifany, may be either identical to one another or different from any other.

R⁶² represents, independently of each other, an alkyl group substitutedby one or more halogen atoms. The number of carbon atoms is within therange of usually 1 or more and usually 6 or less, preferably 3 or less.The halogen atoms are not particularly limited in their kinds, althoughfluorine atoms are preferred in terms of electrochemical stability. Thenumber of substituent halogen atoms of the alkyl group is usually 1 ormore, preferably 2 or more. The upper limit depends on the number ofcarbon atoms the alkyl group has, although being usually 6 or less,preferably 4 or less. Examples of R⁶² include fluoromethyl group,difluoromethyl group, trifluoromethyl group, 1-fluoroethyl group,2-fluoroethyl group, 2,2-difluoroethyl group, 2,2,2-trifluoroethylgroup, pentafluoroethyl group, heptafluoropropyl group, etc. Preferredamong these are fluorine-substituted alkyl groups whose number of carbonatoms is 1 or more and 6 or less, especially preferable beingfluorine-substituted alkyl groups whose number of carbon atoms is 1 ormore and 3 or less. These alkyl groups may be substituted by one or moreother groups. The substituents that the alkyl groups of R⁶² may have arenot particularly limited unless they depart from the gist of thenon-aqueous electrolyte solution of the present invention, althoughalkoxy groups, hydroxy groups, and amino groups are desirable. Z⁶ unitsof R⁶² may be either identical to one another or different from anyother.

Any two or more of R⁶¹ and/or R⁶² may be linked with each other to forma cyclic structure, which decreases the number hydrogen atoms in themolecule and results in suppression of hydrogen-gas generation.

X⁶, the linkage part that links the plural functional groups together,represents a Z⁶-valent hydrocarbon group. The number of carbon atoms iswithin the range of usually 1 or more and usually 6 or less, preferably3 or less. Examples of X⁶ are Z⁶-valent hydrocarbon groups obtained byremoving Z⁶ hydrogen atoms from alkyl groups, such as ethane, propane,n-butane, isobutane, n-pentane, isopentane, and neopentane, or from arylgroups, such as benzene and toluene. These hydrocarbon groups may besubstituted by one or more other groups. The substituents that the alkylgroups of X⁶ may have are not particularly limited unless they departfrom the gist of the non-aqueous electrolyte solution of the presentinvention, although halogen atoms, alkoxy groups, hydroxy groups, andamino groups are desirable.

The molecular weight of the compound (IIc) is usually 150 or larger,preferably 180 or larger, and usually 1000 or smaller, preferably 500 orsmaller. The molecular weight equaling or exceeding the aforementionedlower limit is indispensable in order to satisfy the structure of thegeneral formula (IIc). On the other hand, if it exceeds the upper limit,the compound molecules may not cluster densely during formation ofcomplex coating, bringing about degradation when stored in a dischargedstate.

Examples of the compound (IIc) are enumerated below, although theselections are not limited to the following examples. Any compound canbe used unless it runs counter to the gist of the present invention.

Z⁶=2:

Z⁶=3:

Z⁶=4:

Among the compounds enumerated above, preferable compounds as thecompound (IIc) are (A-1), (A-2), (A-3) or (B-1), especially preferablebeing (A-1), (A-2) and (A-3).

In the non-aqueous electrolyte solution (IIc), the compounds (IIc) maybe used either any one singly or in combination of any two or more atarbitrary proportion.

The concentration of the compound (IIc) in the non-aqueous electrolytesolution (IIc) is within the range of usually 0.01 weight % or higher,preferably 0.05 weight % or higher, especially preferably 0.1 weight %or higher, and usually 4 weight % or lower, preferably 3 weight % orlower, more preferably 2 weight % or lower, especially preferably 1weight % or lower. If the proportion of the compound (IIc) is too low,gas inhibitory effect may not emerge adequately. On the other hand, ifthe proportion is too high, discharging storage characteristics of thebattery tends to decline. When two or more compounds (IIc) are usedcombinedly, the total proportion of the compounds (IIc) is required tomeet the aforementioned range.

It is not clear why using the non-aqueous electrolyte solution (IIc)containing the compound (IIc) as the electrolyte solution of a secondarybattery, especially of a lithium secondary battery, can suppressdegradation during storage in a discharged state and also reduce gasgeneration markedly, although the probable reason is presumed asfollowing.

The non-aqueous electrolyte solution (IIc) causes reaction on thepositive electrode or the negative electrode during initial charging toform organic macromolecule coating. Since the compound used in PatentDocument 7 has a single amide site, i.e., a single reaction site, it mayhave the effect of terminating polymerization reaction. Hence,macromolecularization may not progress to a sufficient degree, resultingin that the solution containing the compound is inferior in stability ofthe organic coating in an electrolyte solution when stored in adischarged state compared to a solution without the compound. On theother hand, since the compound (IIc) contained in the non-aqueouselectrolyte solution (IIc) have plural amide sites, i.e., pluralreaction sites, it can keep causing polymerization reaction withoutterminating it. This is presumably because the non-aqueous electrolytesolution (IIc) can form favorable coating that is capable of inhibitinggas generation without impairing stability during storage in adischarged state.

If the concentration of the compound (IIc) in the non-aqueouselectrolyte solution (IIc) is too low, it may produce little effectbecause it cannot produce an adequate amount of coating. On the otherhand, if the concentration is too high, it may cause unfavorable effectson other battery characteristics such as discharging storagecharacteristics because it produces such an abundance of coating thatthe properties of coating may be altered. Consequently, theconcentration range defined in the present invention is consideredappropriate.

<Others>

When the non-aqueous electrolyte solution (II) contains two or more ofthe compound (IIa), the compound (IIb), and the compound (IIc), thetotal concentration of compounds (II) with respect to the non-aqueouselectrolyte solution (II) is within the range of usually 0.01 weight %or higher, preferably 0.05 weight % or higher, especially preferably 0.1weight % or higher, and usually 5 weight % or lower, preferably 4 weight% or lower, more preferably 3 weight % or lower, especially preferably 2weight % or lower. If the content of the compounds (II) is too low,inhibitory effect of degradation under high voltage may not appear to anadequate extent. On the other hand, if the proportion is too high,characteristics such as large-current characteristics of the batterytend to decline.

[Unsaturated Cyclic Carbonate Compound (D Ingredient)]

In addition to the aforementioned C ingredient, the non-aqueouselectrolyte solution (II) may preferably contain an unsaturated cycliccarbonate compound as D ingredient. As described above, an unsaturatedcyclic carbonate compound means a compound that has at least onecarbonate structure and at least one carbon-carbon double bond permolecule, at least one cyclic structure per molecule.

Incorporating the unsaturated cyclic carbonate compound into thenon-aqueous electrolyte solution contains can improve storagecharacteristics of the resultant battery. The reason is not clear,although it is presumed that stable protective coating is formed on thenegative electrode surface. If the content is too low, storagecharacteristics cannot be fully improved. Use of an unsaturated cycliccarbonate in an electrolyte solution generally becomes a cause of gasgeneration during storage at high temperature. However, its combined usewith a compound expressed by the Compound II is favorable because itproduces a battery that can inhibit gas generation and improve theshortcomings from the unsaturated cyclic carbonate.

Examples of unsaturated cyclic carbonate compounds are vinylenecarbonate compounds, vinyl ethylene carbonate compounds, and methyleneethylene carbonate compounds.

Examples of vinylene carbonate compounds include vinylene carbonate,methyl vinylene carbonate, ethyl vinylene carbonate, 4,5-dimethylvinylene carbonate, 4,5-diethyl vinylene carbonate, fluoro vinylenecarbonate, and trifluoromethyl vinylene carbonate.

Examples of vinyl ethylene carbonate compounds include vinyl ethylenecarbonate, 4-methyl-4-vinyl ethylene carbonate, 4-ethyl-4-vinyl ethylenecarbonate, 4-n-propyl-4-vinyl ethylene carbonate, 5-methyl-4-vinylethylene carbonate, 4,4-divinyl ethylene carbonate, and 4,5-divinylethylene carbonate.

Examples of methylene ethylene carbonate compounds are methyleneethylene carbonate, 4,4-dimethyl-5-methylene ethylene carbonate, and4,4-diethyl-5-methylene ethylene carbonate.

Among them, preferable unsaturated cyclic carbonate compounds arevinylene carbonate, vinyl ethylene carbonate, especially preferablebeing vinylene carbonate.

These unsaturated cyclic carbonate compounds may be used either any onealone or in combination of two or more in an arbitrary proportion.

When the non-aqueous electrolyte solution (II) contains a unsaturatedcyclic carbonate compound in combination with the aforementionedcompound (IIa) or compound (IIb), its proportion in the non-aqueouselectrolyte solution (II) is within the range of usually 0.01 weight %or higher, preferably 0.1 weight % or higher, especially preferably 0.3weight % or higher, most preferably 0.5 weight % or higher, and usually8 weight % or lower, preferably 4 weight % or lower, especiallypreferably 3 weight % or lower. When two or more unsaturated cycliccarbonate compounds are used combinedly, the total proportion of theunsaturated cyclic carbonate compounds is required to meet theaforementioned range.

When the non-aqueous electrolyte solution (II) contains a unsaturatedcyclic carbonate compound in combination with the aforementionedcompound (IIc), its proportion in the non-aqueous electrolyte solution(II) is within the range of usually 0.01 weight % or higher, preferably0.1 weight % or higher, especially preferably 0.5 weight % or higher,most preferably 1 weight % or higher, and usually 10 weight % or lower,preferably 5 weight % or lower, especially preferably 2.5 weight % orlower. When two or more unsaturated cyclic carbonate compounds are usedcombinedly, the total proportion of the unsaturated cyclic carbonatecompounds is required to meet the aforementioned range.

If the content of the unsaturated cyclic carbonate compound is too low,it may not adequately produce the effect of improving cyclecharacteristics of the battery. Since an unsaturated cyclic carbonatecompound is apt to react with a positive electrode material in the stateof charging, the use of the unsaturated cyclic carbonate compound in thenon-aqueous electrolyte solution generally brings about a problem thatthe amount of gas generation during continuous charging. However, itsuse in combination with the compound (II) is preferable because itprevents the amount of gas generation increasing and improves cyclecharacteristics while inhibiting gas generation. On the other hand, ifthe content of the unsaturated cyclic carbonate compound is too high,there arise tendencies to increase the amount of gas generation duringhigh-temperature storage and to deteriorate discharging characteristicsat low temperature.

When the non-aqueous electrolyte solution (II) contains an unsaturatedcyclic carbonate compound in combination with the aforementionedcompound (II), the weight ratio between the compound (II) and theunsaturated cyclic carbonate compound is usually 1:1-50 in the statewhere the non-aqueous electrolyte solution (II) is prepared. When two ormore unsaturated cyclic carbonate compounds and/or compounds (II) arecombinedly used, the total proportion of the unsaturated cycliccarbonate compounds and/or the compounds (II) is required to meet theaforementioned range.

[Other Ingredients]

Besides the aforementioned electrolyte, the non-aqueous solvent, and thecompound (II) (C ingredient), in addition to the unsaturated cycliccarbonate compound (D ingredient) used according to need, thenon-aqueous electrolyte solution (II) may contain other ingredientsunless they impair the effects of the present invention. Examples ofother ingredients are various conventionally-known assistants such asanti-overcharging agent, acid removers, dehydrator, and fire retardant.The details of anti-overcharging agent and other assistants, such astheir selections and their amounts to be used, are the same as explainedabove in connection with non-aqueous electrolyte solution (I).

[Production Method of Non-Aqueous Electrolyte Solution (II)]

The non-aqueous electrolyte solution of the present invention (II) canbe prepared by dissolving the aforementioned electrolyte into theaforementioned non-aqueous solvent together with other ingredients usedaccording to need, such as the compound (II) (C ingredient), theunsaturated cyclic carbonate compound (D ingredient) and otherassistants. Before preparing the non-aqueous electrolyte solution (II),it is desired to dewater in advance the individual ingredients such asthe non-aqueous solvent. Specifically, it is desirable to carry outdewatering until their water contents become usually 50 ppm or lower,preferably 30 ppm or lower. The methods of dewatering can be selectedarbitrarily, examples of which methods are heating under a reducedpressure or passing through a molecular sieve.

The non-aqueous electrolyte solution (II) may also be prepared in asemisolid state through gelation using a gelatinizer such asmacromolecules. The ratio of the non-aqueous electrolyte solution (II)with respect to the semisolid electrolyte is within the range of usually30 weight % or higher, preferably 50 weight % or higher, more preferably75 weight % or higher, and usually 99.95 weight % or lower, preferably99 weight % or lower, more preferably 98 weight % or lower. If the ratioof the non-aqueous electrolyte solution (II) is too high, thenon-aqueous electrolyte solution (II) may hardly be secured and istherefore prone to cause leakage. On the other hand, if the ratio of thenon-aqueous electrolyte solution (II) is too low, the battery may bedeficient in charge and discharge efficiencies and capacity.

[3: Lithium Secondary Battery]

Next, the lithium secondary battery of the present invention will beexplained.

The lithium secondary battery of the present invention comprises, asminimum components, a negative electrode and a positive electrode thatare capable of absorbing and desorbing lithium ions in addition to theaforementioned non-aqueous electrolyte solution of the presentinvention.

That is to say, the lithium secondary battery of the present inventionhas the same arrangement as those of the conventionally-known lithiumsecondary batteries expect the non-aqueous electrolyte solution: it isusually constituted by layering the positive electrode and the negativeelectrode with a porous membrane (separator) interposed between, whichseparator is impregnated with the non-aqueous electrolyte solution ofthe present invention, and containing these components in a case. Theshape of the lithium secondary battery of the present invention is notparticularly limited and may be any shape, such as cylindrical type,square type, laminated type, coin type, large-sized type, etc.

[Positive Electrode Active Material]

Examples of the positive electrode active material are oxides oftransition metals, composite oxides of transition metals and lithium(lithium transition metal composite oxides), sulfides of transitionmetals, inorganic compounds such as metal oxides, lithium metal, lithiumalloys, and their mixtures. Specific examples are: transition metaloxides such as MnO, V₂O₅, V₆O₁₃, and TiO₂; lithium cobalt compositeoxides whose basic composition is expressed by LiCoO₂; lithium nickelcomposite oxides expressed by LiNiO₂; lithium manganese composite oxideexpressed by LiMn₂O₄ or LiMnO₂; lithium transition metal compositeoxides such as lithium nickel manganese cobalt composite oxide, andlithium nickel cobalt aluminum composite oxide; transition metalsulfides such as TiS and FeS; metal oxides such as SnO₂ and SiO₂. Amongthem, lithium transition metal composite oxides, specifically, lithiumcobalt composite oxide, lithium nickel composite oxide, lithium cobaltnickel composite oxide, lithium nickel manganese cobalt composite oxide,and lithium nickel cobalt aluminum composite oxide are preferably usedbecause they realize both large capacity and high cycle characteristics.Part of cobalt, nickel or manganese site of the lithium transition metalcomposite oxides may preferably be replaced with metals such as Al, Ti,V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, and Zr because it stabilizesthe structure. These positive electrode active materials may be usedeither any one singly or in combination of any two or more at anarbitrary ratio.

[Negative Electrode Active Material]

As the negative electrode active material, it is possible to usematerials capable of absorbing and desorbing lithium's, such ascarbonaceous materials, metal compounds, lithium metal and lithiumalloys. Preferable among them are carbonaceous materials, especiallypreferable being graphite and surface-covered graphite with carbonmaterial that is more amorphous compared to graphite. These negativeelectrode active materials may be used either any one singly or incombination of any two or more at an arbitrary ratio.

Desirable Graphite is the following: the d value (interlayer distance)of the lattice plane (002 plane) obtained by X-ray diffraction accordingto Gakushin method (a method stipulated by Japan Society for thePromotion of Science) is usually between 0.335-0.340 nm, preferablybetween 0.335-0.338 nm, especially preferably between 0.335-0.337 nm.The crystallite size (Lc) obtained by X-ray diffraction according toGakushin method is usually 30 nm or larger, preferably 50 nm or larger,especially preferably 100 nm or larger. The ash content is usually 1weight % or lower, preferably 0.5 weight % or lower, especiallypreferably 0.1 weight % or lower.

Desirable surface-covered graphite with amorphous carbon is thefollowing: graphite whose d value (interlayer distance) of the latticeplane (002 plane) obtained by X-ray diffraction is between 0.335-0.338nm is used as core material, and its surface is coated with carbonmaterial that has a larger d value (interlayer distance) of the latticeplane (002 plane) obtained by X-ray diffraction than the core material.Besides, the proportion of the core material and the carbon materialwhose d value (interlayer distance) of the lattice plane (002 plane)obtained by X-ray diffraction is larger than that of the core materialis between 99/1-80/20 in terms of weight ratio. With the above material,it is possible to produce a negative electrode that has high capacityand hardly reacts with the electrolyte solution.

The particle diameter of the carbonaceous material in terms of mediandiameter obtained by laser diffraction/scattering method is usually 1 μmor larger, preferably 3 μm or larger, more preferably 5 μm or larger,most preferably 7 μm or larger, and usually 100 μm or smaller,preferably 50 μm or smaller, more preferably 40 μm or smaller, mostpreferably 30 μm or smaller.

The specific surface area of the carbonaceous material by means of BETmethod is usually 0.3 m²/g or larger, preferably 0.5 m²/g or larger,more preferably 0.7 m²/g or larger, most preferably 0.8 m²/g or larger,and usually 25 m²/g or smaller, preferably 20 m²/g or smaller, morepreferably 15 m²/g or smaller, most preferably 10 m²/g or smaller.

When the carbonaceous material is measured by Raman spectrum analysisusing argon laser beam, the R value expressed by the ratio ofI_(B)/I_(A) where I_(A) represents the intensity of peak P_(A), which isdetected within a range of between 1570-1620 cm⁻¹, and I_(B) representsthe intensity of peak P_(B), which is detected within a range of between1300-1400 cm⁻¹, is preferably within the range of between 0.01-0.7.Also, desirable half-value width of the peak within the range of between1570-1620 cm⁻¹ is usually 26 cm⁻¹ or smaller, preferably 25 cm⁻¹ orsmaller.

Examples of metal compounds capable of absorbing and desorbing lithiumare compounds containing metals such as Ag, Al, Ba, Bi, Cu, Ga, Ge, In,Ni, P, Pb, Sb, Si, Sn, Sr, Zn, etc. These metals may be used in anystate, such as simple substance, oxide, or lithium alloy. In the presentinvention, it is preferable to use a compound containing an elementselected from Al, Ge, Si and Sn, especially preferable being a oxide orlithium alloy of a metal selected from Al, Si and Sn.

The metal compounds capable of absorbing and desorbing lithium and theiroxides and alloys with lithium generally has a larger capacity per unitof weight compared to carbon materials, notably graphite, and istherefore suitable for a lithium secondary battery, which requireshigher energy density.

[Production Method of Electrodes]

The electrodes may be produced according to the usual methods. Accordingto one of the methods, the negative electrode or positive electrodeactive material is combined with binder, thickener, conductive material,solvent, etc., and made into the form of slurry, and the obtained slurryis applied onto a collector and subjected to drying followed bypressing.

As the binder for binding the active material, any material can be usedas long as it is stable both to solvent used in the electrode productionand to the electrolyte solution. Examples of the binder are fluorineresins such as poly vinylidene fluoride and polytetrafluoroethylene,polyolefins such as polyethylene and polypropylene, unsaturated polymersand their copolymers such as styrene butadiene rubber, isoprene rubber,butadiene rubber, etc., acrylic acid polymers and their copolymers suchas ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer,etc.

For the sake of improving mechanical strength and electricalconductivity, the electrodes may contain materials such as thickener,conductive material, and filler.

Examples of thickener are carboxylmethyl cellulose, methyl cellulose,hydroxy methyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidizedstarch, phosphatized starch, and casein.

Examples of conductive material are metal materials, such as copper andnickel, and carbon materials, such as graphite and carbon black.

The active material may be mixed with other materials such as binder andconductive material, and the mixture may be directly roll-molded into asheet electrode, compression-molded into a pellet electrode, or formedinto an electrode-material thin layer on the collector by means ofevaporation, spattering, plating, or a like method.

When graphite is used as the negative electrode active material, thedensity of the negative electrode active material layer after drying andpressing is usually 1.45 g/cm³ or higher, preferably 1.55 g/cm³ orhigher, especially preferably 1.60 g/cm³ or higher.

The density of the positive electrode active material layer after dryingand pressing is usually 3.0 g/cm³ or higher.

The collector is usually made of a metal or an alloy. Specifically,examples of the negative-electrode collector are copper and its alloys,nickel and its alloys, stainless steel, etc., among which copper and itsalloys are preferred. Examples of the positive electrode collector arealuminum, titanium, tantalum, and their alloys, among which aluminum andits alloys are preferred. In order to improve the bindability of itssurface to the active material layer formed thereon, the collectorsurface may preferably undergo roughening processing in advance.Examples of surface roughening methods are: blasting processing; rollingwith a rough-surfaced roll; mechanical polishing methods in which thecollector surface is polished with an abrasive cloth or paper onto whichabradant particles are adhered, a whetstone, an emery buff, a wire brushequipped with steel wires, etc; electropolishing methods; and chemicalpolishing methods.

Besides, with a view to decrease collector weight and improve energydensity per battery weight, it is also possible to use a perforated-typecollector such as an expanded metal or a punching metal. This type ofcollector is freely adjustable in its weight by means of adjusting itsperforation rate. Besides, when the active material layer is formed onboth sides of this type of collector, the active material layer isriveted at these perforations and becomes resistant to exfoliation.However, if the perforation rate is too high, bond strength may ratherdecrease because the contact area between the active material layer andthe collector becomes too small.

The thickness of the collector is usually 1 μm or larger, preferably 5μm or larger, and usually 100 μm or smaller, preferably 50 μm orsmaller. If it is too thick, the capacity of the whole battery maydecrease markedly. On the other hand, if it is too thin, it may bedifficult to handle.

[Separator]

In order to prevent the occurrence of a short circuit, a separator isusually interposed between the positive electrode and negativeelectrode. The separator is usually impregnated with the non-aqueouselectrolyte solution of the present invention.

The separator, although not limited particularly in its material or itsshape, may preferably be a porous sheet or a nonwoven fabric that isexcellent in liquid retention and is made of a material stable to thenon-aqueous electrolyte solution of the present invention. Examples ofthe separator material are polyolefins such as polyethylene andpolypropylene, as well as polytetrafluoroethylene and polyether sulfone,among which polyolefin is preferred.

The thickness of the separator is usually 1 μm or larger, preferably 5μm or larger, more preferably 10 μm or larger, and usually 50 μm orsmaller, preferably 40 μm or smaller, more preferably 30 μm or smaller.If the separator is too thin, insulation performance and mechanicalstrength may deteriorate, while if it is too thick, not only batterycharacteristics such as rate characteristics may deteriorate but alsoenergy density as the whole battery may decline.

The porosity of the separator is usually 20% or higher, preferably 35%or higher, more preferably 45% or higher, and usually 90% or lower,preferably 85% or lower, more preferably 75% or lower. If the porosityis too low, rate characteristics tend to deteriorate due to increase infilm resistance. If the porosity is too high, insulation performancetends to decline due to decrease in mechanical strength of theseparator.

The average pore diameter of the separator is usually 0.5 μm or smaller,preferably 0.2 μm or smaller, and usually 0.05 μm or larger. Excessivelylarge average pore diameter tends to bring about a short circuit, whileexcessively small average pore diameter may cause deterioration in ratecharacteristics due to increase in film resistance.

[Outer Casing]

The outer casing used for the lithium secondary battery of the presentinvention may be made of any material, examples of which includenickel-plated iron, stainless steel, aluminum and its alloys, nickel,titanium, etc.

EXAMPLES

Hereinafter, the present invention will be explained in further detailwith reference to Examples, although the following Examples are usedsimply for explaining the present invention in detail. The presentinvention is not limited to the following Examples unless it runscounter to its gist.

Examples/Comparative-Examples Group (Ia)

Procedures explained in each of the following Examples and ComparativeExamples were carried out to thereby prepare a non-aqueous electrolytesolution, produce a lithium secondary battery using the resultantnon-aqueous electrolyte solution, and evaluate the obtained lithiumsecondary battery.

Production and evaluation procedures of a lithium secondary battery,which are common to the Examples and the Comparative Examples, areexplained in advance.

[Battery Production and Evaluation Procedures]

Production of Negative Electrode:

94 weight parts of natural graphite powder, whose d value of the latticeplane (002 plane) obtained by X-ray diffraction is 0.336 nm, whosecrystallite size (Lc) is 652 nm, whose ash content is 0.07 weight %,whose median diameter according to laser diffraction/scattering methodis 12 μm, whose specific surface area according to BET method is 7.5m²/g, whose R value (=I_(B)/I_(A)) according to Raman spectrum analysisusing argon ion laser light 0.12, and whose half-value width of the peakwithin the range of between 1570-1620 cm⁻¹ is 19.9 cm⁻¹, was mixed with6 weight parts of poly vinylidene fluoride and made into the form ofslurry under the presence of N-methyl-2-pyrrolidone. Onto a surface of acopper foil with the thickness of 12 μm, the obtained slurry was applieduniformly, dried and pressed in such a manner that the density of thenegative electrode active layer be 1.6 g/cm³, thereby a negativeelectrode being obtained.

Production of Positive Electrode:

85 weight parts of LiCoO₂, 6 weight parts of carbon black and 9 weightparts of poly vinylidene fluoride (trade mark “KF-1000”, manufactured byKureha Kagaku Corp.) were mixed together and made into the form ofslurry under the presence of N-methyl-2-pyrrolidone. Onto the bothsurfaces of an aluminum foil with the thickness of 15 μm, the obtainedslurry was applied uniformly, dried and pressed in such a manner thatthe density of the positive electrode active layer be 3.0 g/cm³, therebya positive electrode being obtained.

Production of Lithium Secondary Battery:

The thus-obtained positive electrode and negative electrodes, togetherwith separators made of polyethylene, were layered in the order of anegative electrode, a separator, a positive electrode, a separator, anda negative electrode, to produce a battery element. The battery elementwas inserted into a bag formed with laminated film of aluminum (40 μm inthickness), whose both faces were coated with resin layers, with theterminals of the positive electrode and negative electrodes sticking outfrom the bag. The bag was filled with a non-aqueous electrolytesolution, which was prepared in each of the Examples and ComparativeExamples described below, and then vacuum-sealed to produce a sheet-typebattery (a lithium secondary battery of each of the Examples and theComparative Examples).

Capacity Evaluation:

The lithium secondary battery of each of the Examples and theComparative Examples was sandwiched between glass plates in such amanner that the electrodes were brought into more intimate contact witheach other, and subject to the following procedures. At 25° C., thebattery was charged with a constant current corresponding to 0.2 C untilit reached 4.2 V, and then discharged with 0.2 C constant current untilit reached 3 V. The steps were carried out for three cycles to stabilizethe battery. In the fourth cycle, the battery was charged with aconstant current of 0.5 C until it reached 4.2 V, then charged under 4.2V constant voltage until the current value reached 0.05 C, anddischarged with 0.2 C constant current until it reached 3 V. Thusinitial discharging capacity was obtained.

In the description, 1 C represents a current value for discharging abase capacity of the battery in one hour, and 0.2 C represents ⅕ of thecurrent value.

Evaluation of Low-Temperature Cycle Characteristics:

After the capacity evaluation test, the lithium secondary battery wasplaced at 0° C. and subjected to a cycle test in which the battery wascharged with a 0.5 C constant current until it reached 4.2 V, thencharged under 4.2 V constant voltage until the current value reached0.05 C, and discharged with 0.2 C constant current until it reached 3 V.With respect to the discharging capacity at the first cycle, thedischarging capacity after the fiftieth cycle was determined on apercentage basis.

Evaluation of Room-Temperature Cycle Characteristics:

Subsequently to the capacity evaluation test, the lithium secondarybattery was placed at 25° C. and subjected to a cycle test in which thebattery was charged with a 0.5 C constant current until it reached 4.2V, then charged under 4.2 V constant voltage until the current valuereached 0.05 C, and discharged with a 1 C constant current until itreached 3 V. With respect to the discharging capacity before the cycletest, the discharging capacity after the 300th cycle was determined on apercentage basis.

Evaluation of Continuous Charging Characteristics:

After the capacity evaluation test, the lithium secondary battery wassubmerged in an ethanol bath to measure its volume. The battery wasplaced at 60° C. and charged with a 0.5 C constant current until itreached 4.25 V, followed by constant voltage charging that continued forone week. The battery was then cooled and submerged in an ethanol bathto measure its volume. Based on the amount of change in volume beforeand after the continuous charging, the amount of generated gas wasdetermined.

After the measurement of the amount of generated gas, the battery wasplaced at 25° C. and discharged with 0.2 C constant current until itreached 3 V to thereby obtain residual capacity after the continuouscharging test. With respect to the discharging capacity before thecontinuous charging test, the residual capacity after the continuouscharging was determined on a percentage basis.

Example (Ia-1)

In an atmosphere of dry argon, 97 weight parts of the mixture ofethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate(2:4:4 in volume ratio) was mixed with 2 weight parts of vinylenecarbonate, serving as an unsaturated cyclic carbonate compound, and oneweight part of (methyl)(2-methoxyethyl) carbonate, serving as a compound(Ia). In the resultant mixture, well-dried LiPF₆ was dissolved in theproportion of 1.0 mol/liter. Thus, a non-aqueous electrolyte solution(the non-aqueous electrolyte solution of Example (Ia-1)) was prepared.The obtained non-aqueous electrolyte solution was subjected to theaforementioned procedures to thereby produce the lithium secondarybattery (the lithium secondary battery of Example (Ia-1)).

Comparative Example (Ia-1)

98 weight parts of the mixture of ethylene carbonate, ethyl methylcarbonate, and dimethyl carbonate (2:4:4 in volume ratio) was mixed with2 weight parts of vinylene carbonate, serving as an unsaturated cycliccarbonate compound. In the resultant mixture, well-dried LiPF₆ wasdissolved in the proportion of 1.0 mol/liter. Thus, a non-aqueouselectrolyte solution (the non-aqueous electrolyte solution ofComparative Example (Ia-1)) was prepared. The obtained non-aqueouselectrolyte solution was subjected to the aforementioned procedures tothereby produce the lithium secondary battery (the lithium secondarybattery of Comparative Example (Ia-1)).

Comparative Example (Ia-2)

99 weight parts of the mixture of ethylene carbonate, ethyl methylcarbonate, and dimethyl carbonate (2:4:4 in volume ratio) was mixed withone weight part of (methyl)(2-methoxyethyl)carbonate. In the resultantmixture, well-dried LiPF₆ was dissolved in the proportion of 1.0mol/liter. Thus, a non-aqueous electrolyte solution (the non-aqueouselectrolyte solution of Comparative Example (Ia-2)) was prepared. Theobtained non-aqueous electrolyte solution was subjected to theaforementioned procedures to thereby produce the lithium secondarybattery (the lithium secondary battery of Comparative Example (Ia-2)).

Comparative Example (Ia-3)

In the mixture of ethylene carbonate, ethyl methyl carbonate, anddimethyl carbonate (2:4:4 in volume ratio), well-dried LiPF₆ wasdissolved in the proportion of 1.0 mol/liter. Thus, a non-aqueouselectrolyte solution (the non-aqueous electrolyte solution ofComparative Example (Ia-3)) was prepared. The obtained non-aqueouselectrolyte solution was subjected to the aforementioned procedures tothereby produce the lithium secondary battery (the lithium secondarybattery of Comparative Example (Ia-3)).

Example (Ia-2)

96 weight parts of the mixture of ethylene carbonate, ethyl methylcarbonate, and dimethyl carbonate (2:4:4 in volume ratio) was mixed with2 weight parts of vinylene carbonate, serving as an unsaturated cycliccarbonate compound, and 2 weight parts of(methyl)(2-methoxyethyl)carbonate, serving as a compound (Ia). In theresultant mixture, well-dried LiPF₆ was dissolved in the proportion of1.0 mol/liter. Thus, a non-aqueous electrolyte solution (the non-aqueouselectrolyte solution of Example (Ia-2)) was prepared. The obtainednon-aqueous electrolyte solution was subjected to the aforementionedprocedures to thereby produce the lithium secondary battery (the lithiumsecondary battery of Example (Ia-2)).

Example (Ia-3)

97 weight parts of the mixture of ethylene carbonate, ethyl methylcarbonate, and dimethyl carbonate (2:4:4 in volume ratio) was mixed with2 weight parts of vinylene carbonate, serving as an unsaturated cycliccarbonate compound, and one weight part of bis(2-methoxyethyl)carbonate,serving as a compound (Ia). In the resultant mixture, well-dried LiPF₆was dissolved in the proportion of 1.0 mol/liter. Thus, a non-aqueouselectrolyte solution (the non-aqueous electrolyte solution of Example(Ia-3)) was prepared. The obtained non-aqueous electrolyte solution wassubjected to the aforementioned procedures to thereby produce thelithium secondary battery (the lithium secondary battery of Example(Ia-3)).

[Evaluation Results of Batteries]

The lithium secondary batteries of Examples (Ia-1)-(Ia-3) andComparative Examples (Ia-1)-(Ia-3) obtained according to theaforementioned procedures were subjected to the evaluation oflow-temperature and room-temperature cycle characteristics and theevaluation of continuous charging characteristics. The evaluationresults are shown in Tables (Ia-1)-(Ia-3).

TABLE 1 Table (Ia-1) Unsaturated Cyclic Compound (Ia) Carbonate CompoundMixed Mixed Amount Amount (weight (weight Selection part) Selectionpart) Example (Ia-1)

1 Vinylene Carbonate 2 Comparative — — Vinylene 2 Example Carbonate(Ia-1) Comparative Example (Ia-2)

1 — — Comparative — — — — Example (Ia-3) Example (Ia-2)

2 Vinylene Carbonate 2 Example (Ia-3)

1 Vinylene Carbonate 2

TABLE (Ia-2) Low-Temperature Cycle Room-Temperature CycleCharacteristics (%) Characteristics (%) Example (Ia-1) 95 89 Comparative87 88 Example (Ia-1) Comparative 94 80 Example (Ia-2) Comparative 94 79Example (Ia-3) Example (Ia-2) 95 88 Example (Ia-3) 94 88

TABLE (Ia-3) Amount of Generated Residual Capacity after Gas (ml)Continuous Charging (%) Example (Ia-1) 0.48 96 Comparative 0.76 89Example (Ia-1) Comparative 0.46 88 Example (Ia-3)

As is evident from Tables (Ia-1), (Ia-2), the lithium secondarybatteries of Examples (Ia-1)-(Ia-3) are superior in cyclecharacteristics even at low temperature while maintaining high cyclecharacteristics at room temperature, compared with the lithium secondarybatteries of Comparative Examples (Ia-1)-(Ia-3).

Besides, as is evident from Table (Ia-3), the lithium secondarybatteries of Examples (Ia-1)-(Ia-3) generate little amount of gas duringcontinuous charging and are superior in battery characteristics aftercontinuous charging, compared with the lithium secondary batteries ofComparative Examples (Ia-1)-(Ia-3).

Consequently, according to the definitions of the present invention, asthe lithium secondary batteries of Examples (Ia-1)-(Ia-3), it is clearlypossible to produce a battery that exhibits excellent cyclecharacteristics both at room temperature and at low temperature, isstable under high-temperature, high-voltage conditions, and is alsoexcellent in storage characteristics.

Examples/Comparative-Examples Group (Ib)

Procedures explained in each of the following Examples and ComparativeExamples were carried out to thereby prepare a non-aqueous electrolytesolution, produce a lithium secondary battery using the resultantnon-aqueous electrolyte solution, and evaluate the obtained lithiumsecondary battery.

Production and evaluation procedures of a lithium secondary battery,which are common to the Examples and the Comparative Examples, areexplained in advance.

[Battery Production and Evaluation Procedures]

Production of Negative Electrode:

94 weight parts of natural graphite powder, whose d value of the latticeplane (002 plane) obtained by X-ray diffraction is 0.336 nm, whosecrystallite size (Lc) is 652 nm, whose ash content is 0.07 weight %,whose median diameter according to laser diffraction/scattering methodis 12 μm, whose specific surface area according to BET method is 7.5m²/g, whose R value (=I_(B)/I_(A)) according to Raman spectrum analysisusing argon ion laser light 0.12, and whose half-value width of the peakwithin the range of between 1570-1620 cm⁻¹ is 19.9 cm⁻¹, was mixed with6 weight parts of poly vinylidene fluoride and made into the form ofslurry under the presence of N-methyl-2-pyrrolidone. Onto a surface of acopper foil with the thickness of 12 μm, the obtained slurry was applieduniformly, dried and pressed in such a manner that the density of thenegative electrode active layer be 1.6 g/cm³, thereby a negativeelectrode being obtained.

Production of Positive Electrode:

85 weight parts of LiCoO₂, 6 weight parts of carbon black and 9 weightparts of poly vinylidene fluoride (trade mark “KF-1000”, manufactured byKureha Kagaku Corp.) were mixed together and made into the form ofslurry under the presence of N-methyl-2-pyrrolidone.

Onto the both surfaces of an aluminum foil with the thickness of 15 μm,the obtained slurry was applied uniformly, dried and pressed in such amanner that the density of the positive electrode active layer be 3.0g/cm³, thereby a positive electrode being obtained.

Production of Lithium Secondary Battery:

The thus-obtained positive electrode and negative electrodes, togetherwith separators made of polyethylene, were layered in the order of anegative electrode, a separator, a positive electrode, a separator, anda negative electrode, to produce a battery element. The battery elementwas inserted into a bag formed with laminated film of aluminum (40 μm inthickness), whose both faces were coated with resin layers, with theterminals of the positive electrode and negative electrodes sticking outfrom the bag. The bag was filled with a non-aqueous electrolytesolution, which was prepared in each of the Examples and ComparativeExamples described below, and then vacuum-sealed to produce a sheet-typebattery (a lithium secondary battery of each of the Examples and theComparative Examples).

Capacity Evaluation:

The lithium secondary battery of each of the Examples and theComparative Examples was sandwiched between glass plates in such amanner that the electrodes were brought into more intimate contact witheach other, and subject to the following procedures. At 25° C., thebattery was charged with a constant current corresponding to 0.2 C untilit reached 4.2 V, and then discharged with 0.2 C constant current untilit reached 3V. The steps were carried out for three cycles to stabilizethe battery. In the fourth cycle, the battery was charged with aconstant current of 0.5 C until it reached 4.2 V, then charged under 4.2V constant voltage until the current value reached 0.05 C, anddischarged with 0.2 C constant current until it reached 3 V. Thusinitial discharging capacity was obtained.

In the description, 1 C represents a current value for discharging abase capacity of the battery in one hour, and 0.2 C represents ⅕ of thecurrent value.

Evaluation of Continuous Charging Characteristics:

After the capacity evaluation test, the lithium secondary battery wassubmerged in an ethanol bath to measure its volume. The battery wasplaced at 60° C. and charged with a 0.5 C constant current until itreached 4.25 V, followed by constant voltage charging that continued forone week.

The battery was then cooled and submerged in an ethanol bath to measureits volume. Based on the amount of change in volume before and after thecontinuous charging, the amount of generated gas was determined.

After the measurement of the amount of gas generation, the battery wasplaced at 25° C. and discharged with 0.2 C constant current until itreached 3 V to thereby obtain residual capacity after the continuouscharging test. With respect to the discharging capacity before thecontinuous charging test, the residual capacity after the continuouscharging was determined on a percentage basis.

Evaluation of High-Temperature-Storage Characteristics:

After the capacity evaluation test, the lithium secondary battery wascharged with a 0.5 C constant current until it reached 4.2 V, and thencharged under 4.2 V constant voltage until the current value reached0.05 C, followed by storage at 85° C. for 3 days. Subsequently, thebattery was well-cooled to 25° C. and subjected to discharging with 0.2C constant current until it reached 3 V to thereby obtain residualcapacity after the storage test. With respect to the dischargingcapacity before the storage test, the residual capacity after thestorage test was determined on a percentage basis.

Evaluation of Cycle Characteristics:

After the capacity evaluation test, the lithium secondary battery wasplaced at 25° C. and subjected to a cycle test in which the battery wascharged with a 0.5 C constant current until it reached 4.2 V, thencharged under 4.2 V constant voltage until the current value reached0.05 C, and discharged with a 1 C constant current until it reached 3 V.With respect to the discharging capacity before the cycle test, thedischarging capacity after the 300th cycle was determined on apercentage basis.

Example (Ib-1)

In an atmosphere of dry argon, 96 weight parts of the mixture ofethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate(2:4:4 in volume ratio) was mixed with 2 weight parts of vinylenecarbonate, serving as an unsaturated cyclic carbonate compound, and 2weight parts of methane sulfonyl fluoride, serving as a compound (Ib).In the resultant mixture, well-dried LiPF₆ was dissolved in theproportion of 1.0 mol/liter. Thus, a non-aqueous electrolyte solution(the non-aqueous electrolyte solution of Example (Ib-1)) was prepared.The obtained non-aqueous electrolyte solution was subjected to theaforementioned procedures to thereby produce the lithium secondarybattery (the lithium secondary battery of Example (Ib-1)).

Example (Ib-2)

In an atmosphere of dry argon, 97 weight parts the mixture of ethylenecarbonate, ethyl methyl carbonate, and dimethyl carbonate (2:4:4 involume ratio) was mixed with 2 weight parts of vinylene carbonate,serving as an unsaturated cyclic carbonate compound, and one weight partof methane sulfonyl fluoride, serving as a compound (Ib). In theresultant mixture, well-dried LiPF₆ was dissolved in the proportion of1.0 mol/liter. Thus, a non-aqueous electrolyte solution (the non-aqueouselectrolyte solution of Example (Ib-2)) was prepared. The obtainednon-aqueous electrolyte solution was subjected to the aforementionedprocedures to thereby produce the lithium secondary battery (the lithiumsecondary battery of Example (Ib-2)).

Example (Ib-3)

In an atmosphere of dry argon, 97 weight parts of the mixture ofethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate(2:4:4 in volume ratio) was mixed with 2 weight parts of vinylenecarbonate, serving as an unsaturated cyclic carbonate compound, and oneweight part of ethane sulfonyl fluoride, serving as a compound (Ib). Inthe resultant mixture, well-dried LiPF₆ was dissolved in the proportionof 1.0 mol/liter. Thus, a non-aqueous electrolyte solution (thenon-aqueous electrolyte solution of Example (Ib-3)) was prepared. Theobtained non-aqueous electrolyte solution was subjected to theaforementioned procedures to thereby produce the lithium secondarybattery (the lithium secondary battery of Example (Ib-3)).

Example (Ib-4)

In an atmosphere of dry argon, 97 weight parts of the mixture ofethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate(2:4:4 in volume ratio) was mixed with 2 weight parts of vinylenecarbonate, serving as an unsaturated cyclic carbonate compound, and oneweight part of propane sulfonyl fluoride, serving as a compound (Ib). Inthe resultant mixture, well-dried LiPF₆ was dissolved in the proportionof 1.0 mol/liter. Thus, a non-aqueous electrolyte solution (thenon-aqueous electrolyte solution of Example (Ib-4)) was prepared. Theobtained non-aqueous electrolyte solution was subjected to theaforementioned procedures to thereby produce the lithium secondarybattery (the lithium secondary battery of Example (Ib-4)).

Example (Ib-5)

In an atmosphere of dry argon, 97.5 weight parts of the mixture ofethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate(2:4:4 in volume ratio) was mixed with 2 weight parts of vinylenecarbonate, serving as an unsaturated cyclic carbonate compound, and 0.5weight part of methane sulfonyl fluoride, serving as a compound (Ib). Inthe resultant mixture, well-dried LiPF₆ was dissolved in the proportionof 1.0 mol/liter. Thus, a non-aqueous electrolyte solution (thenon-aqueous electrolyte solution of Example (Ib-5)) was prepared. Theobtained non-aqueous electrolyte solution was subjected to theaforementioned procedures to thereby produce the lithium secondarybattery (the lithium secondary battery of Example (Ib-5)).

Comparative Example (Ib-1)

98 weight parts of the mixture of ethylene carbonate, ethyl methylcarbonate, and dimethyl carbonate (2:4:4 in volume ratio) was mixed with2 weight parts of vinylene carbonate, serving as an unsaturated cycliccarbonate compound. In the resultant mixture, well-dried LiPF₆ wasdissolved in the proportion of 1.0 mol/liter. Thus, a non-aqueouselectrolyte solution (the non-aqueous electrolyte solution ofComparative Example (Ib-1)) was prepared. The obtained non-aqueouselectrolyte solution was subjected to the aforementioned procedures tothereby produce the lithium secondary battery (the lithium secondarybattery of Comparative Example (Ib-1)).

Comparative Example (Ib-2)

96 weight parts of the mixture of ethylene carbonate, ethyl methylcarbonate, and dimethyl carbonate (2:4:4 in volume ratio) was mixed with2 weight parts of vinylene carbonate, serving as an unsaturated cycliccarbonate compound, and 2 weight parts of benzene sulfonyl fluoride asan additive. In the resultant mixture, well-dried LiPF₆ was dissolved inthe proportion of 1.0 mol/liter. Thus, a non-aqueous electrolytesolution (the non-aqueous electrolyte solution of Comparative Example(Ib-2)) was prepared. The obtained non-aqueous electrolyte solution wassubjected to the aforementioned procedures to thereby produce thelithium secondary battery (the lithium secondary battery of ComparativeExample (Ib-2)).

Comparative Example (Ib-3)

96 weight parts of the mixture of ethylene carbonate, ethyl methylcarbonate, and dimethyl carbonate (2:4:4 in volume ratio) was mixed with2 weight parts of vinylene carbonate, serving as an unsaturated cycliccarbonate compound, and 2 weight parts of p-toluene sulfonyl fluoride asan additive. In the resultant mixture, well-dried LiPF₆ was dissolved inthe proportion of 1.0 mol/liter. Thus, a non-aqueous electrolytesolution (the non-aqueous electrolyte solution of Comparative Example(Ib-3)) was prepared. The obtained non-aqueous electrolyte solution wassubjected to the aforementioned procedures to thereby produce thelithium secondary battery (the lithium secondary battery of ComparativeExample (Ib-3)).

Comparative Example (Ib-4)

In an atmosphere of dry argon, 98 weight parts of the mixture ofethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate(2:4:4 in volume ratio) was mixed with 2 weight parts of methanesulfonyl fluoride, serving as a compound (Ib). In the resultant mixture,well-dried LiPF₆ was dissolved in the proportion of 1.0 mol/liter. Thus,a non-aqueous electrolyte solution (the non-aqueous electrolyte solutionof Comparative Example (Ib-4)) was prepared. The obtained non-aqueouselectrolyte solution was subjected to the aforementioned procedures tothereby produce the lithium secondary battery (the lithium secondarybattery of Comparative Example (Ib-4)).

[Evaluation Results of Batteries]

The lithium secondary batteries of Examples (Ib-1)-(Ib-5) andComparative Examples (Ib-1)-(Ib-4) obtained according to theaforementioned procedures were subjected to the evaluation of continuouscharging characteristics, high-temperature-storage characteristics, andcycle characteristics. The evaluation results are shown in Table (Ib-1)and Table (Ib-2).

TABLE 4 Table (Ib-1) Cyclic Carbonate Compound (Ib) or Additive CompoundMixed with Amount Unsaturated (weight Bond Selection part) (weight part)Example (Ib-1) CH₃—SO₂F 2 2 Example (Ib-2) CH₃—SO₂F 1 2 Example (Ib-3)C₂H₅—SO₂F 1 2 Example (Ib-4) C₃H₇—SO₂F 1 2 Example (Ib-5) CH₃—SO₂F 0.5 2Comparative — 0 2 Example (Ib-1) Comparative Example (Ib-2)

2 2 Comparative Example (Ib-3)

2 2 Comparative CH₃—SO₂F 2 0 Example (Ib-4)

TABLE (Ib-2) Residual Residual Capacity Capacity Cycle Amount of afterafter High- Charac- Generated Continuous Temperature teristics Gas (ml)Charging(%) Storage (%) (%) Example (Ib-1) 0.59 96 80 88 Example (Ib-2)0.60 96 80 89 Example (Ib-3) 0.57 95 81 89 Example (Ib-4) 0.55 95 82 —Example (Ib-5) 0.60 95 79 — Comparative 0.76 89 75 88 Example (Ib-1)Comparative 0.73 88 67 — Example (Ib-2) Comparative 1.28 83 63 — Example(Ib-3) Comparative 0.52 90 73 79 Example (Ib-4)

As is evident from Table (Ib-1) and Table (Ib-2), the lithium secondarybatteries of Examples (Ib-1)-(Ib-5) generate little amount of gas duringcontinuous charging and are superior in battery characteristics aftercontinuous charging, battery characteristics after high-temperaturestorage, and cycle characteristics, compared with the lithium secondarybatteries of Comparative Examples (Ib-1)-(Ib-4).

Examples/Comparative-Examples Group (Ic)

Procedures explained in each of the following Examples and ComparativeExamples were carried out to thereby prepare a non-aqueous electrolytesolution, produce a lithium secondary battery using the resultantnon-aqueous electrolyte solution, and evaluate the obtained lithiumsecondary battery.

Production and evaluation procedures of a lithium secondary battery,which are common to the Examples and the Comparative Examples, areexplained in advance.

[Battery Production and Evaluation Procedures]

85 weight parts of LiCoO₂, 6 weight parts of carbon black and 9 weightparts of poly vinylidene fluoride (trade mark “KF-1000”, manufactured byKureha Kagaku Corp.) were mixed together and made into the form ofslurry under the presence of N-methyl-2-pyrrolidone. Onto the both facesof an aluminum foil with the thickness of 15 μm, the obtained slurry wasapplied uniformly, dried and pressed in such a manner that the densityof the positive electrode active layer be 3.0 g/cm³, thereby a positiveelectrode being obtained.

Production of Negative Electrode:

94 weight parts of natural graphite powder, whose d value of the latticeplane (002 plane) obtained by X-ray diffraction is 0.336 nm, whosecrystallite size (Lc) is 652 nm, whose ash content is 0.07 weight %,whose median diameter according to laser diffraction/scattering methodis 12 μm, whose specific surface area according to BET method is 7.5m²/g, whose R value (=I_(B)/I_(A)) according to Raman spectrum analysisusing argon ion laser light 0.12, and whose half-value width of the peakwithin the range of between 1570-1620 cm⁻¹ is 19.9 cm⁻¹, was mixed with6 weight parts of poly vinylidene fluoride and made into the form ofslurry under the presence of N-methyl-2-pyrrolidone. Onto a surface of acopper foil with the thickness of 12 μm, the obtained slurry was applieduniformly, dried and pressed in such a manner that the density of thenegative electrode active layer be 1.6 g/cm³, thereby a negativeelectrode being obtained.

Production of Lithium Secondary Battery:

The thus-obtained positive electrode and negative electrodes, togetherwith separators made of polyethylene, were layered in the order of anegative electrode, a separator, a positive electrode, a separator, anda negative electrode, to produce a battery element. The battery elementwas inserted into a bag formed with laminated film of aluminum (40 μm inthickness), whose both faces were coated with resin layers, with theterminals of the positive electrode and negative electrodes sticking outfrom the bag. The bag was filled with a non-aqueous electrolytesolution, which was prepared in each of the Examples and ComparativeExamples described below, and then vacuum-sealed to produce a sheet-typebattery (a lithium secondary battery of each of the Examples and theComparative Examples).

[Initial Evaluation]

The lithium secondary battery of each of the Examples and theComparative Examples was sandwiched between glass plates in such amanner that the electrodes were brought into more intimate contact witheach other, and subject to the following procedures. At 25° C., thebattery was charged with a constant current corresponding to 0.2 C untilit reached 4.2 V, and then discharged with 0.2 C constant current untilit reached 3 V. The steps were carried out for three cycles to stabilizethe battery. In the description, 1 C represents a current value fordischarging a base capacity of the battery in one hour, and 0.2 Crepresents ⅕ of the current value. Subsequently, the volume of thebattery was measured according to Archimedes' method.

[Evaluation of Continuous Charging Characteristics]

After the initial evaluation, the lithium secondary battery wascontinuously charged under 4.3 V constant voltage for 7 days while keptat the constant temperature of 60° C. After the battery was well-coolednaturally, the battery volume after continuous charging was measuredaccording to Archimedes' method, and the variation from the batteryvolume at the initial evaluation was obtained as a gas amount duringcontinuous charging. Reducing the gas amount enables the design of abattery in which the occurrence of swelling during continuous chargingis inhibited. Subsequently, the battery was discharged with 0.2 Cconstant current until it reached 3 V, then charged with a 0.5 Cconstant current until it reached 4.2 V, and charged under 4.2 Vconstant voltage until the current value reached 0.05 C. The battery wasthen discharged with a 1 C constant current until it reached 3 V toobtain a capacity in 1 C discharging after continuous charging.Increasing the capacity in 1 C discharging enables the design of abattery in which degradation is inhibited.

Example (Ic-1)

In an atmosphere of dry argon, 975 weight parts of the mixture ofethylene carbonate and ethyl methyl carbonate (1:2 in volume ratio),serving as non-aqueous solvents, was mixed with 20 weight parts ofvinylene carbonate (VC), serving as an unsaturated cyclic carbonatecompound, and then combined with 5 weight parts of the compoundexpressed by the aforementioned chemical formula (7) (additive B1). Tothe resultant mixture, well-dried LiPF₆ was added as an electrolyte inthe proportion of 1.0 mol/liter and dissolved. Thus, a non-aqueouselectrolyte solution (the non-aqueous electrolyte solution of Example(Ic-1)) was prepared. The obtained non-aqueous electrolyte solution wassubjected to the aforementioned procedures to thereby produce thelithium secondary battery (the lithium secondary battery of Example(Ic-1)).

Example (Ic-2)

In an atmosphere of dry argon, 975 weight parts of the mixture ofethylene carbonate and ethyl methyl carbonate (1:2 in volume ratio),serving as non-aqueous solvents, was mixed with 20 weight parts ofvinylene carbonate (VC), serving as an unsaturated cyclic carbonatecompound, and then combined with 5 weight parts of the compoundexpressed by the aforementioned chemical formula (8) (additive B2). Tothe resultant mixture, well-dried LiPF₆ was added as an electrolyte inthe proportion of 1.0 mol/liter and dissolved. Thus, a non-aqueouselectrolyte solution (the non-aqueous electrolyte solution of Example(Ic-2)) was prepared. The obtained non-aqueous electrolyte solution wassubjected to the aforementioned procedures to thereby produce thelithium secondary battery (the lithium secondary battery of Example(Ic-2)).

Example (Ic-3)

In an atmosphere of dry argon, 975 weight parts of the mixture ofethylene carbonate and ethyl methyl carbonate (1:2 in volume ratio),serving as non-aqueous solvents, was mixed with 20 weight parts ofvinylene carbonate (VC), serving as an unsaturated cyclic carbonatecompound, and then combined with 5 weight parts of the compoundexpressed by the aforementioned chemical formula (11) (additive B3). Tothe resultant mixture, well-dried LiPF₆ was added as an electrolyte inthe proportion of 1.0 mol/liter and dissolved. Thus, a non-aqueouselectrolyte solution (the non-aqueous electrolyte solution of Example(Ic-3)) was prepared. The obtained non-aqueous electrolyte solution wassubjected to the aforementioned procedures to thereby produce thelithium secondary battery (the lithium secondary battery of Example(Ic-3)).

Example (Ic-4)

In an atmosphere of dry argon, 975 weight parts of the mixture ofethylene carbonate and ethyl methyl carbonate (1:2 in volume ratio),serving as non-aqueous solvents, was mixed with 20 weight parts ofvinylene carbonate (VC), serving as an unsaturated cyclic carbonatecompound, and then combined with 5 weight parts of the compoundexpressed by the aforementioned chemical formula (12) (additive B4). Tothe resultant mixture, well-dried LiPF₆ was added as an electrolyte inthe proportion of 1.0 mol/liter and dissolved. Thus, a non-aqueouselectrolyte solution (the non-aqueous electrolyte solution of Example(Ic-4)) was prepared. The obtained non-aqueous electrolyte solution wassubjected to the aforementioned procedures to thereby produce thelithium secondary battery (the lithium secondary battery of Example(Ic-4)).

Example (Ic-5)

In an atmosphere of dry argon, 975 weight parts of the mixture ofethylene carbonate and ethyl methyl carbonate (1:2 in volume ratio),serving as non-aqueous solvents, was mixed with 20 weight parts ofvinylene carbonate (VC), serving as an unsaturated cyclic carbonatecompound, and then combined with 5 weight parts of the compoundexpressed by the aforementioned chemical formula (13) (additive B5). Tothe resultant mixture, well-dried LiPF₆ was added as an electrolyte inthe proportion of 1.0 mol/liter and dissolved. Thus, a non-aqueouselectrolyte solution (the non-aqueous electrolyte solution of Example(Ic-5)) was prepared. The obtained non-aqueous electrolyte solution wassubjected to the aforementioned procedures to thereby produce thelithium secondary battery (the lithium secondary battery of Example(Ic-5)).

Example (Ic-6)

In an atmosphere of dry argon, 975 weight parts of the mixture ofethylene carbonate and ethyl methyl carbonate (1:2 in volume ratio),serving as non-aqueous solvents, was mixed with 20 weight parts ofvinylene carbonate (VC), serving as an unsaturated cyclic carbonatecompound, and then combined with 5 weight parts of the compoundexpressed by the aforementioned chemical formula (19) (additive B6). Tothe resultant mixture, well-dried LiPF₆ was added as an electrolyte inthe proportion of 1.0 mol/liter and dissolved. Thus, a non-aqueouselectrolyte solution (the non-aqueous electrolyte solution of Example(Ic-6)) was prepared. The obtained non-aqueous electrolyte solution wassubjected to the aforementioned procedures to thereby produce thelithium secondary battery (the lithium secondary battery of Example(Ic-6)).

Example (Ic-7)

In an atmosphere of dry argon, 975 weight parts of the mixture ofethylene carbonate and ethyl methyl carbonate (1:2 in volume ratio),serving as non-aqueous solvents, was mixed with 20 weight parts ofvinylene carbonate (VC), serving as an unsaturated cyclic carbonatecompound, and then combined with 5 weight parts of the compoundexpressed by the aforementioned chemical formula (20) (additive B7). Tothe resultant mixture, well-dried LiPF₆ was added as an electrolyte inthe proportion of 1.0 mol/liter and dissolved. Thus, a non-aqueouselectrolyte solution (the non-aqueous electrolyte solution of Example(Ic-7)) was prepared. The obtained non-aqueous electrolyte solution wassubjected to the aforementioned procedures to thereby produce thelithium secondary battery (the lithium secondary battery of Example(Ic-7)).

Comparative Example (Ic-1)

In an atmosphere of dry argon, the mixture of ethylene carbonate andethyl methyl carbonate (1:2 in volume ratio), serving as non-aqueoussolvents, was mixed with well-dried LiPF₆ as an electrolyte in theproportion of 1.0 mol/liter and dissolved. Thus, a non-aqueouselectrolyte solution (the non-aqueous electrolyte solution ofComparative Example (Ic-1)) was prepared. The obtained non-aqueouselectrolyte solution was subjected to the aforementioned procedures tothereby produce the lithium secondary battery (the lithium secondarybattery of Comparative Example (Ic-1)).

Comparative Example (Ic-2)

In an atmosphere of dry argon, 980 weight parts of the mixture ofethylene carbonate and ethyl methyl carbonate (1:2 in volume ratio),serving as non-aqueous solvents, was mixed with 20 weight parts ofvinylene carbonate (VC), serving as an unsaturated cyclic carbonatecompound. To the resultant mixture, well-dried LiPF₆ was added as anelectrolyte in the proportion of 1.0 mol/liter and dissolved. Thus, anon-aqueous electrolyte solution (the non-aqueous electrolyte solutionof Comparative Example (Ic-2)) was prepared. The obtained non-aqueouselectrolyte solution was subjected to the aforementioned procedures tothereby produce the lithium secondary battery (the lithium secondarybattery of Comparative Example (Ic-2)).

Comparative Example (Ic-3)

In an atmosphere of dry argon, 995 weight parts of the mixture ofethylene carbonate and ethyl methyl carbonate (1:2 in volume ratio),serving as non-aqueous solvents, was mixed with 5 weight parts of thecompound expressed by the aforementioned chemical formula (7) (additiveB1). To the resultant mixture, well-dried LiPF₆ was added as anelectrolyte in the proportion of 1.0 mol/liter and dissolved. Thus, anon-aqueous electrolyte solution (the non-aqueous electrolyte solutionof Comparative Example (Ic-3)) was prepared. The obtained non-aqueouselectrolyte solution was subjected to the aforementioned procedures tothereby produce the lithium secondary battery (the lithium secondarybattery of Comparative Example (Ic-3)).

Comparative Example (Ic-4)

In an atmosphere of dry argon, 995 weight parts of the mixture ofethylene carbonate and ethyl methyl carbonate (1:2 in volume ratio),serving as non-aqueous solvents, was mixed with 5 weight parts of thecompound expressed by the aforementioned chemical formula (8) (additiveB2). To the resultant mixture, well-dried LiPF₆ was added as anelectrolyte in the proportion of 1.0 mol/liter and dissolved. Thus, anon-aqueous electrolyte solution (the non-aqueous electrolyte solutionof Comparative Example (Ic-4)) was prepared. The obtained non-aqueouselectrolyte solution was subjected to the aforementioned procedures tothereby produce the lithium secondary battery (the lithium secondarybattery of Comparative Example (Ic-4)).

Comparative Example (Ic-5)

In an atmosphere of dry argon, 995 weight parts of the mixture ofethylene carbonate and ethyl methyl carbonate (1:2 in volume ratio),serving as non-aqueous solvents, was mixed with 5 weight parts of thecompound expressed by the aforementioned chemical formula (II) (additiveB3). To the resultant mixture, well-dried LiPF₆ was added as anelectrolyte in the proportion of 1.0 mol/liter and dissolved. Thus, anon-aqueous electrolyte solution (the non-aqueous electrolyte solutionof Comparative Example (Ic-5)) was prepared. The obtained non-aqueouselectrolyte solution was subjected to the aforementioned procedures tothereby produce the lithium secondary battery (the lithium secondarybattery of Comparative Example (Ic-5)).

Comparative Example (Ic-6)

In an atmosphere of dry argon, 995 weight parts of the mixture ofethylene carbonate and ethyl methyl carbonate (1:2 in volume ratio),serving as non-aqueous solvents, was mixed with 5 weight parts of thecompound expressed by the aforementioned chemical formula (12) (additiveB4). To the resultant mixture, well-dried LiPF₆ was added as anelectrolyte in the proportion of 1.0 mol/liter and dissolved. Thus, anon-aqueous electrolyte solution (the non-aqueous electrolyte solutionof Comparative Example (Ic-6)) was prepared. The obtained non-aqueouselectrolyte solution was subjected to the aforementioned procedures tothereby produce the lithium secondary battery (the lithium secondarybattery of Comparative Example (Ic-6)).

Comparative Example (Ic-7)

In an atmosphere of dry argon, 995 weight parts of the mixture ofethylene carbonate and ethyl methyl carbonate (1:2 in volume ratio),serving as non-aqueous solvents, was mixed with 5 weight parts of thecompound expressed by the aforementioned chemical formula (13) (additiveB5). To the resultant mixture, well-dried LiPF₆ was added as anelectrolyte in the proportion of 1.0 mol/liter and dissolved. Thus, anon-aqueous electrolyte solution (the non-aqueous electrolyte solutionof Comparative Example (Ic-7)) was prepared. The obtained non-aqueouselectrolyte solution was subjected to the aforementioned procedures tothereby produce the lithium secondary battery (the lithium secondarybattery of Comparative Example (Ic-7)).

Comparative Example (Ic-8)

In an atmosphere of dry argon, 995 weight parts of the mixture ofethylene carbonate and ethyl methyl carbonate (1:2 in volume ratio),serving as non-aqueous solvents, was mixed with 5 weight parts of thecompound expressed by the aforementioned chemical formula (19) (additiveB6). To the resultant mixture, well-dried LiPF₆ was added as anelectrolyte in the proportion of 1.0 mol/liter and dissolved. Thus, anon-aqueous electrolyte solution (the non-aqueous electrolyte solutionof Comparative Example (Ic-8)) was prepared. The obtained non-aqueouselectrolyte solution was subjected to the aforementioned procedures tothereby produce the lithium secondary battery (the lithium secondarybattery of Comparative Example (Ic-8)).

Comparative Example (Ic-9)

In an atmosphere of dry argon, 995 weight parts of the mixture ofethylene carbonate and ethyl methyl carbonate (1:2 in volume ratio),serving as non-aqueous solvents, was mixed with 5 weight parts of thecompound expressed by the aforementioned chemical formula (20) (additiveB7). To the resultant mixture, well-dried LiPF₆ was added as anelectrolyte in the proportion of 1.0 mol/liter and dissolved. Thus, anon-aqueous electrolyte solution (the non-aqueous electrolyte solutionof Comparative Example (Ic-9)) was prepared. The obtained non-aqueouselectrolyte solution was subjected to the aforementioned procedures tothereby produce the lithium secondary battery (the lithium secondarybattery of Comparative Example (Ic-9)).

[Evaluation Results of Batteries]

The lithium secondary batteries of Examples (Ic-1)-(Ic-7) andComparative Examples (Ic-1)-(Ic-9) obtained according to theaforementioned procedures were subjected to the evaluation of continuouscharging characteristics. The evaluation results are shown in thefollowing Tables (Ic-1)-(Ic-7).

TABLE (Ic-1) (Effects of Combined Use of VC and Additive B1) ComparativeComparative Comparative Example Example (Ic-1) Example (Ic-2) Example(Ic-3) (Ic-1) Ingredients Unsaturated None VC None VC Cyclic CarbonateCompound Compound None None Additive Additive (Ic) B1 B1 Results 1Cafter 33 28 10 63 Continuous Charging (mAh/g) Gas after 0.43 0.49 0.110.34 Continuous Charging (ml)

TABLE (Ic-2) (Effects of Combined Use of VC and Additive B2) ComparativeComparative Comparative Example Example (Ic-1) Example (Ic-2) Example(Ic-4) (Ic-2) Ingredients Cyclic None VC None VC Carbonate Compound withUnsaturated Bond Compound None None Additive Additive (Ic) B2 B2 Results1C after 33 28 22 41 Continuous Charging (mAh/g) Gas after 0.43 0.490.17 0.39 Continuous Charging (ml)

TABLE (Ic-3) (Effects of Combined Use of VC and Additive B3) ComparativeComparative Comparative Example Example (Ic-1) Example (Ic-2) Example(Ic-5) (Ic-3) Ingredients Cyclic None VC None VC Carbonate Compound withUnsaturated Bond Compound None None Additive Additive (Ic) B3 B3 Results1C after 33 28 7 71 Continuous Charging (mAh/g) Gas after 0.43 0.49 0.190.27 Continuous Charging (ml)

TABLE (Ic-4) (Effects of Combined Use of VC and Additive B4) ComparativeComparative Comparative Example Example (Ic-1) Example (Ic-2) Example(Ic-6) (Ic-4) Ingredients Cyclic None VC None VC Carbonate Compound withUnsaturated Bond Compound None None Additive Additive (Ic) B4 B4 Results1C after 33 28 27 74 Continuous Charging (mAh/g) Gas after 0.43 0.490.22 0.39 Continuous Charging (ml)

TABLE (Ic-5) (Effects of Combined Use of VC and Additive B5) ComparativeComparative Comparative Example Example (Ic-1) Example (Ic-2) Example(Ic-7) (Ic-5) Ingredients Cyclic None VC None VC Carbonate Compound withUnsaturated Bond Compound None None Additive Additive (Ic) B5 B5 Results1C after 33 28 12 66 Continuous Charging (mAh/g) Gas after 0.43 0.490.26 0.38 Continuous Charging (ml)

TABLE (Ic-6) (Effects of Combined Use of VC and Additive B6) ComparativeComparative Comparative Example Example (Ic-1) Example (Ic-2) Example(Ic-8) (Ic-6) Ingredients Cyclic None VC None VC Carbonate Compound withUnsaturated Bond Compound None None Additive Additive (Ic) B6 B6 Results1C after 33 28 14 84 Continuous Charging (mAh/g) Gas after 0.43 0.490.18 0.41 Continuous Charging (ml)

TABLE (Ic-7) (Effects of Combined Use of VC and Additive B7) ComparativeComparative Comparative Example Example (Ic-1) Example (Ic-2) Example(Ic-9) (Ic-7) Ingredients Cyclic None VC None VC Carbonate Compound withUnsaturated Bond Compound None None Additive Additive (Ic) B7 B7 Results1C after 33 28 6 42 Continuous Charging (mAh/g) Gas after 0.43 0.49 0.160.39 Continuous Charging (ml)

The following findings are derived from Table (Ic-1).

As in Comparative Example (Ic-2), the use of VC increases the gas amountafter continuous charging, compared to Comparative Example (Ic-1) inwhich VC was not used. This is presumably because VC is vulnerable tooxidation. As the result, the addition of VC decreases the 1 C capacityafter continuous charging.

Also, as in Comparative Example (Ic-3), the use of additive B1 (thecompound expressed by chemical formula (7)) inhibits the gas amountafter continuous charging, compared to Comparative Example (Ic-1) inwhich additive B1 was not used. This is presumably because additive B1inhibits the decomposition of the electrolyte solution. On the otherhand, the 1C capacity after continuous charging decreases. This ispresumably because the coating formed increases its resistance.

Consequently, when either A ingredient or B ingredient is used singly,battery characteristics may deteriorate.

In contrast to this, as in Example (Ic-1), the concurrent use of Aingredient and B ingredient dramatically improves 1C capacity aftercontinuous charging, compared with Comparative Examples (Ic-1)-(Ic-3).This is presumably because B ingredient inhibits the decomposition of Aingredient while the coating formed from A ingredient inhibits theformation of coating from B ingredient, as a result of which the batterybecomes stable even during continuous charging.

It is also apparent from Tables (Ic-2)-(Ic-7), as Table (Ic-1), that thesingle use of either A ingredient or B ingredient worsenscharacteristics while the combined use of these ingredients dramaticallyimproves 1C capacity after continuous charging.

Examples/Comparative-Examples Group (IIa)

Procedures explained in each of the following Examples and ComparativeExamples were carried out to thereby prepare a non-aqueous electrolytesolution, produce a lithium secondary battery using the resultantnon-aqueous electrolyte solution, and evaluate the obtained lithiumsecondary battery.

Production and evaluation procedures of a lithium secondary battery,which are common to the Examples and the Comparative Examples, areexplained in advance.

[Battery Production and Evaluation Procedures]

Production of Negative Electrode:

94 weight parts of natural graphite powder, whose d value of the latticeplane (002 plane) obtained by X-ray diffraction is 0.336 nm, whosecrystallite size (Lc) is 652 nm, whose ash content is 0.07 weight %,whose median diameter according to laser diffraction/scattering methodis 12 μm, whose specific surface area according to BET method is 7.5m²/g, whose R value (=I_(B)/I_(A)) according to Raman spectrum analysisusing argon ion laser light 0.12, and whose half-value width of the peakwithin the range of between 1570-1620 cm⁻¹ is 19.9 cm⁻¹, was mixed with6 weight parts of poly vinylidene fluoride and made into the form ofslurry under the presence of N-methyl-2-pyrrolidone. Onto a surface of acopper foil with the thickness of 12 μm, the obtained slurry was applieduniformly, dried and pressed in such a manner that the density of thenegative electrode active layer be 1.6 g/cm³, thereby a negativeelectrode being obtained.

Production of Positive Electrode:

85 weight parts of LiCoO₂, 6 weight parts of carbon black and 9 weightparts of poly vinylidene fluoride (trade mark “KF-1000”, manufactured byKureha Kagaku Corp.) were mixed together and made into the form ofslurry under the presence of N-methyl-2-pyrrolidone. Onto the bothsurfaces of an aluminum foil with the thickness of 15 μm, the obtainedslurry was applied uniformly, dried and pressed in such a manner thatthe density of the positive electrode active layer be 3.0 g/cm³, therebya positive electrode being obtained.

Production of Lithium Secondary Battery:

The thus-obtained positive electrode and negative electrodes, togetherwith separators made of polyethylene, were layered in the order of anegative electrode, a separator, a positive electrode, a separator, anda negative electrode, to produce a battery element. The battery elementwas inserted into a bag formed with laminated film of aluminum (40 μm inthickness), whose both faces were coated with resin layers, with theterminals of the positive electrode and negative electrodes sticking outfrom the bag. The bag was filled with a non-aqueous electrolytesolution, which was prepared in each of the Examples and ComparativeExamples described below, and then vacuum-sealed to produce a sheet-typebattery (a lithium secondary battery of each of the Examples and theComparative Examples).

Capacity Evaluation:

The lithium secondary battery of each of the Examples and theComparative Examples was sandwiched between glass plates in such amanner that the electrodes were brought into more intimate contact witheach other, and subject to the following procedures. At 25° C., thebattery was charged with a constant current corresponding to 0.2 C untilit reached 4.2 V, and then discharged with 0.2 C constant current untilit reached 3 V. The steps were carried out for three cycles to stabilizethe battery. In the fourth cycle, the battery was charged with aconstant current of 0.5 C until it reached 4.2 V, then charged under 4.2V constant voltage until the current value reached 0.05 C, anddischarged with 0.2 C constant current until it reached 3 V. Thusinitial discharging capacity was obtained.

In the description, 1 C represents a current value for discharging abase capacity of the battery in one hour, and 0.2 C represents ⅕ of thecurrent value.

Evaluation of Continuous Charging Characteristics:

After the capacity evaluation test, the lithium secondary battery wassubmerged in an ethanol bath to measure its volume. The battery wasplaced at 60° C. and charged with a 0.5 C constant current until itreached 4.25 V, followed by constant voltage charging that continued forone week.

The battery was then cooled and submerged in an ethanol bath to measureits volume. Based on the amount of change in volume before and after thecontinuous charging, the amount of generated gas was determined.

After the measurement of the amount of gas generation, the battery wasplaced at 25° C. and discharged with 0.2 C constant current until itreached 3 V to thereby obtain residual capacity after the continuouscharging test. With respect to the discharging capacity before thecontinuous charging test, the residual capacity after the continuouscharging was determined on a percentage basis.

Evaluation of High-Temperature-Storage Characteristics:

After the capacity evaluation test, the lithium secondary battery wascharged with a 0.5 C constant current until it reached 4.2 V, and thencharged under 4.2 V constant voltage until the current value reached0.05 C, followed by storage at 85° C. for 3 days. Subsequently, thebattery was well-cooled to 25° C. and subjected to discharging with 0.2C constant current until it reached 3 V to thereby obtain residualcapacity after the storage test. With respect to the dischargingcapacity before the storage test, the residual capacity after thestorage test was determined on a percentage basis.

Evaluation of Cycle Characteristics:

After the capacity evaluation test, the lithium secondary battery wasplaced at 25° C. and subjected to a cycle test in which the battery wascharged with a 0.5 C constant current until it reached 4.2 V, thencharged under 4.2 V constant voltage until the current value reached0.05 C, and discharged with a 1 C constant current until it reached 3 V.With respect to the discharging capacity before the cycle test, thedischarging capacity after the 300th cycle was determined on apercentage basis.

Example (IIa-1)

In an atmosphere of dry argon, 97 weight parts of the mixture ofethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate(2:4:4 in volume ratio) was mixed with 2 weight parts of vinylenecarbonate, serving as an unsaturated cyclic carbonate compound, and oneweight part of 2,4,8,10-tetraoxaspiro [5.5]undecane, serving as acompound (IIa). In the resultant mixture, well-dried LiPF₆ was dissolvedin the proportion of 1.0 mol/liter. Thus, a non-aqueous electrolytesolution (the non-aqueous electrolyte solution of Example (IIa-1)) wasprepared. The obtained non-aqueous electrolyte solution was subjected tothe aforementioned procedures to thereby produce the lithium secondarybattery (the lithium secondary battery of Example (IIa-1)).

Example (IIa-2)

97 weight parts of the mixture of ethylene carbonate, ethyl methylcarbonate, and dimethyl carbonate (2:4:4 in volume ratio) was mixed with2 weight parts of vinylene carbonate, serving as an unsaturated cycliccarbonate compound, and one weight part of3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane, serving as a compound(IIa). In the resultant mixture, well-dried LiPF₆ was dissolved in theproportion of 1.0 mol/liter. Thus, a non-aqueous electrolyte solution(the non-aqueous electrolyte solution of Example (IIa-2)) was prepared.The obtained non-aqueous electrolyte solution was subjected to theaforementioned procedures to thereby produce the lithium secondarybattery (the lithium secondary battery of Example (IIa-2)).

Example (IIa-3)

97.5 weight parts of the mixture of ethylene carbonate, ethyl methylcarbonate, and dimethyl carbonate (2:4:4 in volume ratio) was mixed with2 weight parts of vinylene carbonate, serving as an unsaturated cycliccarbonate compound, and 0.5 weight part of3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane, serving as a compound(IIa). In the resultant mixture, well-dried LiPF₆ was dissolved in theproportion of 1.0 mol/liter. Thus, a non-aqueous electrolyte solution(the non-aqueous electrolyte solution of Example (IIa-3)) was prepared.The obtained non-aqueous electrolyte solution was subjected to theaforementioned procedures to thereby produce the lithium secondarybattery (the lithium secondary battery of Example (IIa-3)).

Example (IIa-4)

97.8 weight parts of the mixture of ethylene carbonate, ethyl methylcarbonate, and dimethyl carbonate (2:4:4 in volume ratio) was mixed with2 weight parts of vinylene carbonate, serving as an unsaturated cycliccarbonate compound, and 0.2 weight part of3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane, serving as a compound(IIa). In the resultant mixture, well-dried LiPF₆ was dissolved in theproportion of 1.0 mol/liter. Thus, a non-aqueous electrolyte solution(the non-aqueous electrolyte solution of Example (IIa-4)) was prepared.The obtained non-aqueous electrolyte solution was subjected to theaforementioned procedures to thereby produce the lithium secondarybattery (the lithium secondary battery of Example (IIa-4)).

Comparative Example (IIa-1)

98 weight parts of the mixture of ethylene carbonate, ethyl methylcarbonate, and dimethyl carbonate (2:4:4 in volume ratio) was mixed with2 weight parts of vinylene carbonate, serving as an unsaturated cycliccarbonate compound. In the resultant mixture, well-dried LiPF₆ wasdissolved in the proportion of 1.0 mol/liter. Thus, a non-aqueouselectrolyte solution (the non-aqueous electrolyte solution ofComparative Example (IIa-1)) was prepared. The obtained non-aqueouselectrolyte solution was subjected to the aforementioned procedures tothereby produce the lithium secondary battery (the lithium secondarybattery of Comparative Example (IIa-1)).

Comparative Example (IIa-2)

97 weight parts of the mixture of ethylene carbonate, ethyl methylcarbonate, and dimethyl carbonate (2:4:4 in volume ratio) was mixed with2 weight parts of vinylene carbonate, serving as an unsaturated cycliccarbonate compound, and one weight part of 1,3-dioxane as an additive.In the resultant mixture, well-dried LiPF₆ was dissolved in theproportion of 1.0 mol/liter. Thus, a non-aqueous electrolyte solution(the non-aqueous electrolyte solution of Comparative Example (IIa-2))was prepared. The obtained non-aqueous electrolyte solution wassubjected to the aforementioned procedures to thereby produce thelithium secondary battery (the lithium secondary battery of ComparativeExample (IIa-2)).

Evaluation Results of Batteries

The lithium secondary batteries of Examples (IIa-1)-(IIa-4) andComparative Examples (IIa-1), (IIa-2) obtained according to theaforementioned procedures were subjected to the evaluation of continuouscharging characteristics, high-temperature-storage characteristics, andcycle characteristics. The evaluation results are shown in the followingTable (IIa).

TABLE (IIa) Residual Residual Capacity Capacity Cycle Amount of afterafter High- Charac- Generated Continuous Temperature teristics Gas (ml)Charging (%) Storage (%) (%) Example (IIa-1) 0.40 94 82 88 Example(IIa-2) 0.45 96 81 92 Example (IIa-3) 0.48 92 80 93 Example (IIa-4) 0.4992 81 91 Comparative 0.76 89 75 88 Example (IIa-1) Comparative 0.65 8872 87 Example (IIa-2)

As is evident from Table (IIa), the lithium secondary batteries ofExamples (IIa-1)-(IIa-4) generate little amount of gas during continuouscharging and are superior in battery characteristics after continuouscharging, battery characteristics after high-temperature storage, andcycle characteristics, compared with the lithium secondary batteries ofComparative Examples (IIa-1), (IIa-2).

Examples/Comparative-Examples Group (IIb)

Procedures explained in each of the following Examples and ComparativeExamples were carried out to thereby prepare a non-aqueous electrolytesolution, produce a lithium secondary battery using the resultantnon-aqueous electrolyte solution, and evaluate the obtained lithiumsecondary battery.

Production and evaluation procedures of a lithium secondary battery,which are common to the Examples and the Comparative Examples, areexplained in advance.

[Battery Production and Evaluation Procedures]

Production of Negative Electrode:

94 weight parts of natural graphite powder, whose d value of the latticeplane (002 plane) obtained by X-ray diffraction is 0.336 nm, whosecrystallite size (Lc) is 652 nm, whose ash content is 0.07 weight %,whose median diameter according to laser diffraction/scattering methodis 12 μm, whose specific surface area according to BET method is 7.5m²/g, whose R value (=I_(B)/I_(A)) according to Raman spectrum analysisusing argon ion laser light 0.12, and whose half-value width of the peakwithin the range of between 1570-1620 cm⁻¹ is 19.9 cm⁻¹, was mixed with6 weight parts of poly vinylidene fluoride and made into the form ofslurry under the presence of N-methyl-2-pyrrolidone. Onto a surface of acopper foil with the thickness of 12 μm, the obtained slurry was applieduniformly, dried and pressed in such a manner that the density of thenegative electrode active layer be 1.6 g/cm³, thereby a negativeelectrode being obtained.

Production of Positive Electrode:

85 weight parts of LiCoO₂, 6 weight parts of carbon black and 9 weightparts of poly vinylidene fluoride (trade mark “KF-1000”, manufactured byKureha Kagaku Corp.) were mixed together and made into the form ofslurry under the presence of N-methyl-2-pyrrolidone. Onto the bothsurfaces of an aluminum foil with the thickness of 15 μm, the obtainedslurry was applied uniformly, dried and pressed in such a manner thatthe density of the positive electrode active layer be 3.0 g/cm³, therebya positive electrode being obtained.

Production of Lithium Secondary Battery:

The thus-obtained positive electrode and negative electrodes, togetherwith separators made of polyethylene, were layered in the order of anegative electrode, a separator, a positive electrode, a separator, anda negative electrode, to produce a battery element. The battery elementwas inserted into a bag formed with laminated film of aluminum (40 μm inthickness), whose both faces were coated with resin layers, with theterminals of the positive electrode and negative electrodes sticking outfrom the bag. The bag was filled with a non-aqueous electrolytesolution, which was prepared in each of the Examples and ComparativeExamples described below, and then vacuum-sealed to produce a sheet-typebattery (a lithium secondary battery of each of the Examples and theComparative Examples).

Capacity Evaluation:

The lithium secondary battery of each of the Examples and theComparative Examples was sandwiched between glass plates in such amanner that the electrodes were brought into more intimate contact witheach other, and subject to the following procedures. At 25° C., thebattery was charged with a constant current corresponding to 0.2 C untilit reached 4.2 V, and then discharged with 0.2 C constant current untilit reached 3 V. The steps were carried out for three cycles to stabilizethe battery. In the fourth cycle, the battery was charged with aconstant current of 0.5 C until it reached 4.2 V, then charged under 4.2V constant voltage until the current value reached 0.05 C, anddischarged with 0.2 C constant current until it reached 3 V. Thusinitial discharging capacity was obtained.

In the description, 1 C represents a current value for discharging abase capacity of the battery in one hour, and 0.2 C represents ⅕ of thecurrent value.

Evaluation of Continuous Charging Characteristics:

After the capacity evaluation test, the lithium secondary battery wassubmerged in an ethanol bath to measure its volume. The battery wasplaced at 60° C. and charged with a 0.5 C constant current until itreached 4.25 V, followed by constant voltage charging that continued forone week.

The battery was then cooled and submerged in an ethanol bath to measureits volume. Based on the amount of change in volume before and after thecontinuous charging, the amount of generated gas was determined.

After the measurement of the amount of gas generation, the battery wasplaced at 25° C. and discharged with 0.2 C constant current until itreached 3 V to thereby obtain residual capacity after the continuouscharging test. With respect to the discharging capacity before thecontinuous charging test, the residual capacity after the continuouscharging was determined on a percentage basis.

Evaluation of High-Temperature-Storage Characteristics:

After the capacity evaluation test, the lithium secondary battery wascharged with a 0.5 C constant current until it reached 4.2 V, and thencharged under 4.2 V constant voltage until the current value reached0.05 C, followed by storage at 85° C. for 3 days. Subsequently, thebattery was well-cooled to 25° C. and subjected to discharging with 0.2C constant current until it reached 3 V to thereby obtain residualcapacity after the storage test. With respect to the dischargingcapacity before the storage test, the residual capacity after thestorage test was determined on a percentage basis.

Example (IIb-1)

In an atmosphere of dry argon, 97 weight parts of the mixture ofethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate(2:4:4 in volume ratio) was mixed with 2 weight parts of vinylenecarbonate, serving as an unsaturated cyclic carbonate compound, and oneweight part of propane-1,3-bis (sulfonyl fluoride), serving as acompound (IIb). In the resultant mixture, well-dried LiPF₆ was dissolvedin the proportion of 1.0 mol/liter. Thus, a non-aqueous electrolytesolution (the non-aqueous electrolyte solution of Example (IIb-1)) wasprepared. The obtained non-aqueous electrolyte solution was subjected tothe aforementioned procedures to thereby produce the lithium secondarybattery (the lithium secondary battery of Example (IIb-1)).

Example (IIb-2)

In an atmosphere of dry argon, 97 weight parts of the mixture ofethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate(2:4:4 in volume ratio) was mixed with 2 weight parts of vinylenecarbonate, serving as an unsaturated cyclic carbonate compound, and oneweight part of 1,1,2,2,3,3-hexafluoropropane-1, 3-bis(sulfonylfluoride), serving as a compound (IIb). In the resultant mixture,well-dried LiPF₆ was dissolved in the proportion of 1.0 mol/liter. Thus,a non-aqueous electrolyte solution (the non-aqueous electrolyte solutionof Example (IIb-2)) was prepared. The obtained non-aqueous electrolytesolution was subjected to the aforementioned procedures to therebyproduce the lithium secondary battery (the lithium secondary battery ofExample (IIb-2)).

Example (IIb-3)

In an atmosphere of dry argon, 97.5 weight parts of the mixture ofethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate(2:4:4 in volume ratio) was mixed with 2 weight parts of vinylenecarbonate, serving as an unsaturated cyclic carbonate compound, and 0.5weight part of propane-1,3-bis (sulfonyl fluoride), serving as acompound (IIb). In the resultant mixture, well-dried LiPF₆ was dissolvedin the proportion of 1.0 mol/liter. Thus, a non-aqueous electrolytesolution (the non-aqueous electrolyte solution of Example (IIb-3)) wasprepared. The obtained non-aqueous electrolyte solution was subjected tothe aforementioned procedures to thereby produce the lithium secondarybattery (the lithium secondary battery of Example (IIb-3)).

Comparative Example (IIb-1)

98 weight parts of the mixture of ethylene carbonate, ethyl methylcarbonate, and dimethyl carbonate (2:4:4 in volume ratio) was mixed with2 weight parts of vinylene carbonate, serving as an unsaturated cycliccarbonate compound. In the resultant mixture, well-dried LiPF₆ wasdissolved in the proportion of 1.0 mol/liter. Thus, a non-aqueouselectrolyte solution (the non-aqueous electrolyte solution ofComparative Example (IIb-1)) was prepared. The obtained non-aqueouselectrolyte solution was subjected to the aforementioned procedures tothereby produce the lithium secondary battery (the lithium secondarybattery of Comparative Example (IIb-1)).

Comparative Example (IIb-2)

96 weight parts of the mixture of ethylene carbonate, ethyl methylcarbonate, and dimethyl carbonate (2:4:4 in volume ratio) was mixed with2 weight parts of vinylene carbonate, serving as an unsaturated cycliccarbonate compound, and 2 weight parts of benzene sulfonyl fluoride asan additive. In the resultant mixture, well-dried LiPF₆ was dissolved inthe proportion of 1.0 mol/liter. Thus, a non-aqueous electrolytesolution (the non-aqueous electrolyte solution of Comparative Example(IIb-2)) was prepared. The obtained non-aqueous electrolyte solution wassubjected to the aforementioned procedures to thereby produce thelithium secondary battery (the lithium secondary battery of ComparativeExample (IIb-2)).

Comparative Example (IIb-3)

96 weight parts of the mixture of ethylene carbonate, ethyl methylcarbonate, and dimethyl carbonate (2:4:4 in volume ratio) was mixed with2 weight parts of vinylene carbonate, serving as an unsaturated cycliccarbonate compound, and 2 weight parts of p-toluene sulfonyl fluoride asan additive. In the resultant mixture, well-dried LiPF₆ was dissolved inthe proportion of 1.0 mol/liter. Thus, a non-aqueous electrolytesolution (the non-aqueous electrolyte solution of Comparative Example(IIb-3)) was prepared. The obtained non-aqueous electrolyte solution wassubjected to the aforementioned procedures to thereby produce thelithium secondary battery (the lithium secondary battery of ComparativeExample (IIb-3)).

[Evaluation Results of Batteries]

The lithium secondary batteries of Examples (IIb-1)-(IIb-3) andComparative Examples (IIb-1)-(IIb-3) obtained according to theaforementioned procedures were subjected to the evaluation of continuouscharging characteristics and high-temperature-storage characteristics.The evaluation results are shown in the following Table (IIb).

TABLE 14 Table (IIb) Residual Residual Compound (IIb) or AdditiveCapacity Capacity Mixed Amount of after after High- Amount GeneratedContinuous Temperature (weight Gas Charging Storage Selection part) (ml)(%) (%) Example (SO₂F)—C₃H₆—(SO₂F) 1 0.49 96 83 (IIb-1) Example(SO₂F)—C₃F₆—(SO₂F) 1 0.51 96 81 (IIb-2) Example (SO₂F)—C₃H₆—(SO₂F) 0.50.52 98 84 (IIb-3) Comparative — 0 0.76 89 75 Example (IIb-1)Comparative Example (IIb-2)

2 0.73 88 67 Comparative Example (IIb-3)

2 1.28 83 63

As is evident from Table (IIb), the lithium secondary batteries ofExamples (IIb-1)-(IIb-3) generate little amount of gas during continuouscharging and are superior in battery characteristics afterhigh-temperature storage, compared with the lithium secondary batteriesof Comparative Examples (IIb-1)-(IIb-3).

Examples/Comparative-Examples Group (IIc)

Procedures explained in each of the following Examples and ComparativeExamples were carried out to thereby prepare a non-aqueous electrolytesolution, produce a lithium secondary battery using the resultantnon-aqueous electrolyte solution, and evaluate the obtained lithiumsecondary battery.

Production and evaluation procedures of a lithium secondary battery,which are common to the Examples and the Comparative Examples, areexplained in advance.

[Battery Production and Evaluation Procedures]

Production of Negative Electrode:

94 weight parts of natural graphite powder, whose d value of the latticeplane (002 plane) obtained by X-ray diffraction is 0.336 nm, whosecrystallite size (Lc) is 652 nm, whose ash content is 0.07 weight %,whose median diameter according to laser diffraction/scattering methodis 12 μm, whose specific surface area according to BET method is 7.5m²/g, whose R value (=I_(B)/I_(A)) according to Raman spectrum analysisusing argon ion laser light 0.12, and whose half-value width of the peakwithin the range of between 1570-1620 cm⁻¹ is 19.9 cm⁻¹, was mixed with6 weight parts of poly vinylidene fluoride and made into the form ofslurry under the presence of N-methyl-2-pyrrolidone. Onto a surface of acopper foil with the thickness of 12 μm, the obtained slurry was applieduniformly, dried and pressed in such a manner that the density of thenegative electrode active layer be 1.6 g/cm³. The resultant plate wascut into the shape of 3.5 cm×2.5 cm to thereby obtain a negativeelectrode.

Production of Positive Electrode:

85 weight parts of LiCoO₂, 6 weight parts of carbon black and 9 weightparts of poly vinylidene fluoride (trade mark “KF-1000”, manufactured byKureha Kagaku Corp.) were mixed together and made into the form ofslurry under the presence of N-methyl-2-pyrrolidone. Onto the bothsurfaces of an aluminum foil with the thickness of 15 μm, the obtainedslurry was applied uniformly and dried, followed by pressing in such amanner that the density of the positive electrode active layer be 3.0g/cm³. The resultant plate was cut into the shape of 3.5 cm×2.5 cm tothereby obtain a positive electrode.

Production of Lithium Secondary Battery:

The thus-obtained positive electrode and negative electrodes, togetherwith separators made of polyethylene, were layered in the order of anegative electrode, a separator, a positive electrode, a separator, anda negative electrode, to produce a battery element. The battery elementwas inserted into a bag formed with laminated film of aluminum (40 μm inthickness), whose both faces were coated with resin layers, with theterminals of the positive electrode and negative electrodes sticking outfrom the bag. The bag was filled with a non-aqueous electrolytesolution, which was prepared in each of the Examples and ComparativeExamples described below, and then vacuum-sealed to produce a sheet-typebattery (a lithium secondary battery of each of the Examples and theComparative Examples).

Initial Evaluation:

The lithium secondary battery of each of the Examples and theComparative Examples was sandwiched between glass plates in such amanner that the electrodes were brought into more intimate contact witheach other, and subject to the following procedures. At 25° C., thebattery was charged with a constant current corresponding to 0.2 C untilit reached 4.2 V, and then discharged with 0.2 C constant current untilit reached 3 V. The steps were carried out for three cycles to stabilizethe battery. In the description, 1 C represents a current value fordischarging a base capacity of the battery in one hour, and 0.2 Crepresents ⅕ of the current value. Subsequently, the volume of thebattery was measured according to Archimedes' method.

Evaluation of Continuous Charging Characteristics:

After the initial evaluation, the lithium secondary battery wascontinuously charged under 4.3 V constant voltage for 7 days while keptat the constant temperature of 60° C. After the battery was well-coolednaturally, the battery volume after continuous charging was measuredaccording to Archimedes' method, and the variation from the batteryvolume at the initial evaluation was obtained as a gas amount duringcontinuous charging. Reducing the gas amount enables the design of abattery in which the occurrence of swelling during continuous chargingis inhibited. Subsequently, the battery was discharged with 0.2 Cconstant current until it reached 3 V, then charged with a 0.5 Cconstant current until it reached 4.2 V, and charged under 4.2 Vconstant voltage until the current value reached 0.05 C. The battery wasthen discharged with a 1 C constant current until it reached 3 V toobtain a capacity in 1 C discharging after continuous charging.Increasing the capacity in 1 C discharging enables the design of abattery in which degradation is inhibited.

Evaluation of High-Temperature-Storage Characteristics:

After the initial evaluation, the lithium secondary battery was chargedwith a 0.5 C constant current until it reached 4.2 V, and then chargedunder 4.2 V constant voltage until the current value reached 0.05 C,after which the battery was stored at 85° C. for 72 hours. After thebattery was well-cooled naturally, the battery volume afterhigh-temperature storage was measured according to Archimedes' method,and the variation from the volume before the storage was determined asthe amount of gas generation. Reducing the gas amount enables the designof a battery in which the occurrence of swelling during continuouscharging is inhibited. Subsequently, the battery was charged with a 0.5C constant current until it reached 4.2 V, then charged under 4.2 Vconstant voltage until the current value reached 0.05 C. The battery wasthen discharged with a 1.0 C constant current until it reached 3 V toobtain a capacity in 1 C discharging after continuous charging.Increasing the capacity in 1 C discharging enables the design of abattery in which degradation is inhibited.

Evaluation of Discharging Storage Characteristics:

After the initial evaluation, the lithium secondary battery was storedat 60° C. and variation in residual voltage was monitored. The elapsedtime while the residual voltage changed from 3 V to 1 V was determinedas a discharging storage time. A battery that shows a longer dischargingstorage time suffers less degradation during discharging and is morestable.

Example (IIc-1)

In an atmosphere of dry argon, 998 weight parts of the mixture ofethylene carbonate and ethyl methyl carbonate (1:2 in volume ratio),serving as non-aqueous solvents, was mixed with 2 weight parts ofN,N′-bis (trifluoroacetyl)piperazine, i.e., the aforementioned examplecompound (A-3), as a compound (Ic). To the resultant mixture, well-driedLiPF₆ was added as an electrolyte in the proportion of 1 mol/liter anddissolved. Thus, a non-aqueous electrolyte solution (the non-aqueouselectrolyte solution of Example (IIc-1)) was prepared. The obtainednon-aqueous electrolyte solution was subjected to the aforementionedprocedures to thereby produce the lithium secondary battery (the lithiumsecondary battery of Example (IIc-1)).

Example (IIc-2)

995 weight parts of the mixture of ethylene carbonate and ethyl methylcarbonate (1:2 in volume ratio), serving as non-aqueous solvents, wasmixed with 5 weight parts of N,N′-bis(trifluoroacetyl)piperazine,serving as a compound (Ic). To the resultant mixture, well-dried LiPF₆was added as an electrolyte in the proportion of 1 mol/liter anddissolved. Thus, a non-aqueous electrolyte solution (the non-aqueouselectrolyte solution of Example (IIc-2)) was prepared. The obtainednon-aqueous electrolyte solution was subjected to the aforementionedprocedures to thereby produce the lithium secondary battery (the lithiumsecondary battery of Example (IIc-2)).

Example (IIc-3)

98 weight parts of the mixture of ethylene carbonate and ethyl methylcarbonate (1:2 in volume ratio), serving as non-aqueous solvents, wasmixed with 2 weight parts of N,N′-bis(trifluoroacetyl)piperazine,serving as a compound (Ic). To the resultant mixture, well-dried LiPF₆was added as an electrolyte in the proportion of 1 mol/liter anddissolved. Thus, a non-aqueous electrolyte solution (the non-aqueouselectrolyte solution of Example (IIc-3)) was prepared. The obtainednon-aqueous electrolyte solution was subjected to the aforementionedprocedures to thereby produce the lithium secondary battery (the lithiumsecondary battery of Example (IIc-3)).

Comparative Example (IIc-1)

To the mixture of ethylene carbonate and ethyl methyl carbonate (1:2 involume ratio), serving as non-aqueous solvents, well-dried LiPF₆ wasadded as an electrolyte in the proportion of 1 mol/liter and dissolved.Thus, a non-aqueous electrolyte solution (the non-aqueous electrolytesolution of Comparative Example (IIc-1)) was prepared. The obtainednon-aqueous electrolyte solution was subjected to the aforementionedprocedures to thereby produce the lithium secondary battery (the lithiumsecondary battery of Comparative Example (IIc-1)).

Comparative Example (IIc-2)

995 weight parts of the mixture of ethylene carbonate and ethyl methylcarbonate (1:2 in volume ratio), serving as non-aqueous solvents, wasmixed with 5 weight parts of N,N-dimethyl trifluoroacetamide as anadditive. To the resultant mixture, well-dried LiPF₆ was added as anelectrolyte in the proportion of 1 mol/liter and dissolved. Thus, anon-aqueous electrolyte solution (the non-aqueous electrolyte solutionof Comparative Example (IIc-2)) was prepared. The obtained non-aqueouselectrolyte solution was subjected to the aforementioned procedures tothereby produce the lithium secondary battery (the lithium secondarybattery of Comparative Example (IIc-2)).

Example (IIc-4)

978 weight parts of the mixture of ethylene carbonate and ethyl methylcarbonate (1:2 in volume ratio), serving as non-aqueous solvents, wasmixed with 20 weight parts of vinylene carbonate, serving as anunsaturated cyclic carbonate compound, and 2 weight parts ofN,N′-bis(trifluoroacetyl)piperazine, serving as a compound (Ic). To theresultant mixture, well-dried LiPF₆ was added as an electrolyte in theproportion of 1 mol/liter and dissolved. Thus, a non-aqueous electrolytesolution (the non-aqueous electrolyte solution of Example (IIc-4)) wasprepared. The obtained non-aqueous electrolyte solution was subjected tothe aforementioned procedures to thereby produce the lithium secondarybattery (the lithium secondary battery of Example (IIc-4)).

Example (IIc-5)

975 weight parts of the mixture of ethylene carbonate and ethyl methylcarbonate (1:2 in volume ratio), serving as non-aqueous solvents, wasmixed with 20 weight parts of vinylene carbonate, serving as anunsaturated cyclic carbonate compound, and 5 weight parts ofN,N′-bis(trifluoroacetyl)piperazine, serving as a compound (Ic). To theresultant mixture, well-dried LiPF₆ was added as an electrolyte in theproportion of 1 mol/liter and dissolved. Thus, a non-aqueous electrolytesolution (the non-aqueous electrolyte solution of Example (IIc-5)) wasprepared. The obtained non-aqueous electrolyte solution was subjected tothe aforementioned procedures to thereby produce the lithium secondarybattery (the lithium secondary battery of Example (IIc-5)).

Comparative Example (IIc-3)

98 weight parts of the mixture of ethylene carbonate and ethyl methylcarbonate (1:2 in volume ratio), serving as non-aqueous solvents, wasmixed with 2 weight parts of vinylene carbonate, serving as anunsaturated cyclic carbonate compound. To the resultant mixture,well-dried LiPF₆ was added as an electrolyte in the proportion of 1mol/liter and dissolved. Thus, a non-aqueous electrolyte solution (thenon-aqueous electrolyte solution of Comparative Example (IIc-3)) wasprepared. The obtained non-aqueous electrolyte solution was subjected tothe aforementioned procedures to thereby produce the lithium secondarybattery (the lithium secondary battery of Comparative Example (IIc-3)).

Comparative Example (IIc-4)

975 weight parts of the mixture of ethylene carbonate and ethyl methylcarbonate (1:2 in volume ratio), serving as non-aqueous solvents, wasmixed with 20 weight parts of vinylene carbonate, serving as anunsaturated cyclic carbonate compound, and 5 weight parts ofN,N-dimethyl trifluoroacetamide as an additive. To the resultantmixture, well-dried LiPF₆ was added as an electrolyte in the proportionof 1 mol/liter and dissolved. Thus, a non-aqueous electrolyte solution(the non-aqueous electrolyte solution of Comparative Example (IIc-4))was prepared. The obtained non-aqueous electrolyte solution wassubjected to the aforementioned procedures to thereby produce thelithium secondary battery (the lithium secondary battery of ComparativeExample (IIc-4)).

[Evaluation Results of Batteries]

The lithium secondary batteries of Examples (IIc-1)-(IIc-5) andComparative Examples (IIc-1)-(IIc-4) obtained according to theaforementioned procedures were subjected to the initial evaluation andthe evaluation of continuous charging characteristics,high-temperature-storage characteristics, and discharging storagecharacteristics. The evaluation results are shown in the following Table(IIc-1) and Table (IIc-2). In column “Additive” of each table, “Additive1”represents N,N-dimethyl trifluoroacetamide, and “Additive 2”represents N,N′-bis (trifluoroacetyl)piperazine, being a compound (IIc).Also, in column “Assistant” of each table, “VC”represents vinylenecarbonate, being an unsaturated cyclic carbonate compound.

TABLE (IIc-1) Compound (IIc) Unsaturated Cyclic Continuous 1C CapacityStorage Gas 1C Capacity or Additive Carbonate Compound Charging Gasafter Generation after Concentration Concentration Generation ContinuousAmount Storage Selection (weight %) Selection (weight %) Amount (ml)Charging (mAh/g) (ml) (mAh/g) Comparative None — None — 0.43 33 0.16 110Example (IIc-1) Comparative Additive 1 0.5 None — 0.38 42 0.07 111Example (IIc-2) Example (IIc-1) Additive 2 0.2 None — 0.28 56 0.09 113Example (IIc-2) Additive 2 0.5 None — 0.22 61 0.06 114 Example (IIc-3)Additive 2 2.0 None — 0.20 59 0.03 110 Comparative None — VC 2.0 0.49 280.37 112 Example (IIc-3) Comparative Additive 1 0.5 VC 2.0 0.45 31 0.32117 Example (IIc-4) Example (IIc-4) Additive 2 0.2 VC 2.0 0.39 58 0.30118 Example (IIc-5) Additive 2 0.5 VC 2.0 0.36 71 0.30 116

TABLE (IIc-2) Compound (IIc) Unsaturated Cyclic Discharging or AdditiveCarbonate Compound Storage Concentration Concentration Time Selection(weight %) Selection (weight %) (hours) Comparative None — None — 212Example (IIc-1) Comparative Additive 1 0.5 None — 89 Example (IIc-2)Example (IIc-2) Additive 2 0.5 None — 210 Comparative None — VC 2.0 334Example (IIc-3) Comparative Additive 1 0.5 VC 2.0 292 Example (IIc-4)Comparative Additive 2 0.5 VC 2.0 362 Example (IIc-5)

As is evident from Table (IIc-1), according to the lithium secondarybattery of each of Examples (IIc-1)-(IIc-3), which uses a non-aqueouselectrolyte solutions with a compound (IIc), the amount of gasgeneration was reduced significantly compared with the lithium secondarybattery of Comparative Example 1, which uses a non-aqueous electrolytesolution without any additive. Also, as is evident from Table (IIc-2),the discharging storage time worsened in the lithium secondary batteryof Comparative Example (IIc-2), which uses a non-aqueous electrolytesolution with a compound that has only a single amide site, while suchworsening during discharging storage was scarcely observed in thelithium secondary battery of Example (IIc-2), which uses a non-aqueouselectrolyte solution with a compound (IIc), i.e., a compound that hastwo amide sites. This is presumably because the use of a compound thathas a single amide site does not produce effective organic coating,resulting in deterioration in characteristics.

Besides, the lithium secondary battery of each of Example (IIc-4) andExample (IIc-5), which uses a non-aqueous electrolyte solution thatcontains a compound (IIc), shows gas inhibitory effect compared with thecase where a non-aqueous electrolyte solution with no additive was used,as in Comparative Example (IIc-3), which uses vinylene carbonate beingan unsaturated cyclic carbonate. Also, as in Comparative Example(IIc-4), when a compound that has only a single amide site was added tothe non-aqueous electrolyte solution, the discharging storage timedeteriorates instead.

[Others]

Up to this point the present invention has been explained in detail withreference to specific embodiments, although to those skilled in the artit is obvious that various modifications can be suggested withoutdeparting from the intention and the scope of the present invention.

The present application is based on each of the descriptions of:Japanese Patent Application No. 2004-124174, which was filed Apr. 20,2004; Japanese Patent Application No. 2004-156209, which was filed May26, 2004; Japanese Patent Application No. 2004-214104, which was filedJul. 22, 2004; Japanese Patent Applications Nos. 2004-229188 and2004-229757, which were filed Aug. 5, 2004; and Japanese PatentApplication No. 2004-301751, which was filed Oct. 15, 2004; and theirentireties are incorporated herewith by reference.

INDUSTRIAL APPLICABILITY

As detailed above, the non-aqueous electrolyte solution of the presentinvention, realizes an excellent lithium secondary battery that has alarge capacity, exhibits high storage characteristics and cyclecharacteristics, and is also capable of inhibiting gas generation. Thepresent invention therefore can be suitably applicable to various fieldsin which lithium secondary batteries are used, such as the field ofelectronic devices. As Examples of the uses, there can be mentionednotebook computers, pen-input personal computers, mobile computers,electronic book players, cellular phones, portable facsimiles, portablecopiers, portable printers, headphone stereos, video movies, liquidcrystal televisions, handy cleaners, portable CDs, mini discs,transceivers, electronic databooks, electronic calculators, memorycards, portable tape recorders, radios, backup power sources, motors,illuminators, toys, game machines, watches, stroboscopes, cameras, etc.

1. A non-aqueous electrolyte solution comprising: a lithium salt; anon-aqueous solvent; and a compound expressed by the following generalformula (IIb)

wherein Z⁵ represents an integer of 2 or larger, X⁵ represents a linkagegroup comprising one or more atoms selected from the group consisting ofa carbon atom, a hydrogen atom, a fluorine atom and an oxygen atom, andthe fluoro sulfonyl group is bound to a carbon atom of the linkagegroup.
 2. The non-aqueous electrolyte solution of claim 1, wherein theconcentration of the compound expressed by the general formula (IIb)with respect to the non-aqueous electrolyte solution is 0.001 weight %to 5 weight %.
 3. The non-aqueous electrolyte solution of claim 1further comprising a cyclic carbonate compound wherein said cycliccarbonate compound has an unsaturated bond and has a concentration of0.01 weight % to 8 weight % with respect to the non-aqueous electrolytesolution.
 4. A lithium secondary battery comprising: a non-aqueouselectrolyte solution; and a positive electrode and a negative electrodecapable of absorbing and desorbing lithium ions; wherein the non-aqueouselectrolyte solution is the non-aqueous electrolyte solution of claim 1.